73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: buzzman351 on September 30, 2022, 06:17:45 AM
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I have set timing, replaced map, coolant sensor, egr, pcv, plugs, wires. the list goes on. it runs good but honestly id like for a mechanic to hook it up to a diagnostic machine and tune it or whatever needs to be done. is that possible?
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As long as you find someone who knows what they're doing..... Not many left
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I feel really ignorant, being the owner of a '89 R30 with TBI that doesn't run, due to code 44.
Is there a diagnostic tool that tunes the fuel delivery system?
Sooner or later I will have to dive into this head long, in the meantime any peripheral info would be appreciated... ;)
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i am no expert by any means. i just search the internet, talk to friends and post here but it says code 44 is lean mixture..does the truck run at all?
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First thing to do is get a fuel pressure gauge on there. You can tee in by removing the fuel filter or by adding a test port.
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Not what I would call 'running', I have to feather the pedal to keep it running. I shot a video of intermittent gas coming out of the injectors.
Re: 44, I recall it saying that the O2 sensor should be replaced.
I fired the parts cannon of new filter and temp sensor.
Cleaned up some ground points.
She went from nothing to the feather routine.
I'll get the gauge on next. Any brand you recommend VZ?
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You can pretty much get anywhere
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For those looking, found this for about 40 bucks.
https://www.amazon.com/dp/B09JFWH98C?psc=1&smid=A2C44ZQAB48D69&ref_=chk_typ_imgToDp
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FYI - Although better than no gauge at all, that's not the best gauge for TBI. GM TBI only runs about 12 PSI. It is better to rely on a gauge with the target pressure roughly mid-scale if possible (e.g., 20 - 30 PSI full-scale calibration).
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Thanks, makes sense. ::)
Maybe I can swap out the gauge head. I'll look at the A/C kit I have.
All the other parts made it look like it would be easy to use.
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I've accumulated various gauge heads over the years and interchange them as necessary. That set looks like it has everything you'll need to tap in at the framerail-mounted fuel filter.
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Thanks bd, I was hoping that I could find a place under the hood.
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You should be able to do that with some head scratching and thoughtful planning. The fuel lines are firmly clamped to the rear of the right cylinder head and are tedious to access. Still, with the correct adaptor, you can tap into the pressure line at the back of the throttle body after you unclamp the lines from the head and move the ignition coil out of the way. To alleviate future effort, you might consider installing a permanent pressure tap in a more convenient location. Otherwise, tapping pressure at the fuel filter is not difficult. Once you figure it out and learn how to keep fuel out of your eyes and armpits it becomes fairly routine. 8)
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I have this piece of equipment. It is designed to insert at the frame rail fuel filter location.
https://www.autotoolworld.com/S-G-Tool-Aid-Corp-37650-Gm-Throttle-Body-Injection-Pressure-Tester-Adapter_p_166653.html?gclid=Cj0KCQjw-fmZBhDtARIsAH6H8qiNbG4nJcVFsu0MGnBJgmCfpZYNScp_-mE2dq28PznE2n0rRvw9X_waAka2EALw_wcB
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I was told during my efi adventure that when the o2 sensor fails, it reads full lean and the system runs very rich. You can probably tell from pulling a plug, rear was worst on mine.
Sent from my iPhone using Tapatalk
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i probably should add that my original TBI was toast so i bought one from a guy that was on a 94 chevrolet. i had to wire a different TPS connector but everything else hooked up as it should
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Finally replaced the O2 sensor, definitely made a difference in that the feathering action takes it to a higher RPM.
Still won't idle
Smells rich
Since I had B+ disco'd there are no codes, so will have to do the feather dance till some get thrown.
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Smells rich, won't idle, did you disconnect the vacuum hose at the EGR valve?
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Not that I'm aware of, will check tomorrow. Thx!
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I am suggesting that you do to see if it is hanging open.
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Got it, thanks!
I looked yesterday, there is a electronic module between it and the source.
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Just pull the hose off of the EGR valve and let it dangle in the wind. See if it affects the way it runs.
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VZ
It definitely changed the way it behaves, tried to idle, I can now feather it to much higher RPMs.
Looks like it's stuck? Any thing else to add?
Thanks buddy!
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You should have no vacuum at the hose to the EGR valve with the engine running. If you do, replace the EGR solenoid.
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In addition to vacuum bleeding past a faulty EGR solenoid, an EGR valve is susceptible to carbon accumulation that can prevent seating of its pintle allowing exhaust to bypass the valve. To check the EGR valve for bypassing, remove it from the manifold and flip it upside-down. The pintle and seat are inside the short steel tube protruding from the base of the valve. Dribble some penetrant (e.g., carb cleaner or penetrating oil) into the open end of the tube without disturbing the valve diaphragm. If the penetrant leaks past the pintle and seat into the underlying chamber, the valve is bypassing and should be replaced. A valve in good condition will not bypass at all. Be sure to install a new gasket.
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Thanks guy, I'm on it!!!
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Finally got the EGR off, with the help of a box end 1/2 inch wrench with a curious 115 degree bend. Custom made with the help of my torch...
Doing the leak down test now.
I can blow air through the module from either of the tubes. Just curious if when power is applied a valve closes.
Napa lists the module as an "Eichlin air filter". ???
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Leak down failed.
Ordered parts, will keep you posted. THANKS!!!!
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There's a small foam filter on the solenoid. I'm not sure exactly what you are working on since this thread says 87 k10 (which is a V10) and you mentioned an R30?
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Yeah sorry, I hijacked a 87 K10 thread with my own silly problems...
It's a '88 1 ton w/454/400 TBI.
Their is a filter on the solenoid.
Q: when the solenoid is energized is there a valve that forced closed?
In the absence of 12v, I am able to blow through either port.
Just wondering if I need a new solenoid.
Thanks!
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The ECM grounds the solenoid to energize it and allow vacuum to the EGR valve.
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Ahh, so normally closed. Thx man!
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Well the last salvo from the parts cannon did not do the trick. New EGR and Control Module.
Same symptoms, won't idle, have to feather the throttle to keep rpm's up, to a point she back fires slightly.
Trying to keep her on long enough to have some codes thrown, none yet.
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It sounded to me like you said eliminating the EGR cured the issue. Not sure what you replaced but if you again unhook the EGR and the problem goes away, there is still an issue there.
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Well disconnecting the EGR made a difference in how it ran, in that I could advance the rpm higher.
It was leaking, so replacement was in order.
I could pass air through the module while disconnected, so that suggested a leak when not energized.
Still waiting for some code.
Since the replacement should I power cycle the ECM?
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Have you confirmed there is no suction at the hose at the EGR valve with the engine running now?
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Yes I did what you suggested earlier, I disco'd the hose off the EGR valve.
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and there is no vacuum present now after you've replaced the solenoid right?
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I am unable to ascertain the answer to that VZ, as I have to feather the throttle to keep it running. I can get an assistant to get me to that point, will keep you in the loop. Thx!
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Do you have an OBDI scan tool?
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No I use the paperclip method.
Funny thing is it hasn't thrown any code this time, the CE light comes on during starting.
I am hoping that feathering the throttle over several times it will stay on.
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We need to see your data, codes are great for doing specific tests but live data shows us what the ecm is seeing. You should get one, there's plenty of cheap options.
If you confirm there is no vacuum present at the EGR and it is not hanging it open, next check for vacuum leaks including the base gasket at the TBI. If okay check fuel pressure.
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Well since the 'atmospheric rivers' have subsided and we're not being washed away, I finally hooked up a pressure gauge and NOTHING.
It's not the best gauge according to bd, 0-100 at 10 lb increments, but no reading at all.
It has a bypass valve, that I pressed while feathering the throttle, and gas cycled through.
Just have a nagging doubt about testing the pump before the tank switch prior to going all in with a new pump. Any thoughts?
TIA!
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Low fuel pressure certainly could cause the symptoms. So could a plugged filter, but if you actually had "zero" fuel pressure, the engine wouldn't start. When you say "it has a bypass valve," do you mean a pressure relief valve? Does the TBI adapter fitting for the gauge tap contain a Schrader or similar check valve, or is it completely open and unrestricted to fuel flow out to the gauge?
For a grassroots validation of the gauge, if you have an air compressor with a regulator valve, set the regulator to 25 PSI then feed pressure directly into the gauge and compare the readings.
Buy, rent, or borrow a proper test gauge with a suitable fuel tap fitting. TBI systems demand proper fuel pressure and adequate flow!
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The bypass is really a pressure relief valve, connected right below the gauge, with a clear tube to see if there is flow.
Regarding the check valve, it appear as a T fitting that the gauge snaps onto like a spring loaded air tool quick connection.
The adapter hose appears to be straight thru to the TBI. I installed it post inline filter.
Yes, I tested it against my air compressor, 10 psi differential at 80 to 90. That alone could count for no reading, yes?
It runs but not by itself, I have to feather the throttle so it must have some pressure.
The inline filter is new, but the internal screen/filter is not.
Is the pressure regulator monitored by the ECM? Could it be stuck open?
I could just connect the gauge to the fuel line post filter and read the pump only.
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Is the pressure regulator monitored by the ECM? Could it be stuck open?
Fuel pressure IS NOT monitored by the ECM. Yes, the pressure regulator could be stuck partially open and returning too much fuel to the tank. You can check that by temporarily pinching off the flexible return line that runs back to the tank. Static fuel pressure output from the in-tank pump with no fuel return should be in the neighborhood of 40-60 PSI, IIRC.
I could just connect the gauge to the fuel line post filter and read the pump only.
Correct.
JP, in order to gain a proper diagnosis and ascertain fuel system health, you absolutely must accurately determine the fuel pressure. Because the fuel pressure of the first-generation TBI is so low (11-12 PSI), deviation from the factory specification of just a few PSI can cause notable drivability problems.
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bd, as usual you are the MAN!
Will do, and will report back ASAP.
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Tape the gauge to your windshield, and go for a drive!
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Wish I could Shiftmeister, she won't run on her own without me feathering the gas pedal.
The test rig has all the right fittings and gauge setup, just the wrong type of gauge.
Going to a industrial liquidator now to source one in a lower range.
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15 PSI (https://www.grainger.com/product/GRAINGER-APPROVED-GRAINGER-APPROVED-Commercial-4FLV6?opr=PDPRRDSP&analytics=dsrrItems_4FLT7)
30 PSI (https://www.grainger.com/product/4FLT8?gucid=N:N:PS:Paid:GGL:CSM-2295:4P7A1P:20501231&gclid=EAIaIQobChMIouT6_6f__QIVXW1vBB0PoAbPEAQYBSABEgKkNvD_BwE&gclsrc=aw.ds)
Etc.
Just add the appropriate fitting to match the hose end of your existing gauge.
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If you can verify your pressure and it is accurate, and you can verify that clamping off the return side helps.. This is the first thing I would check
(http://www.73-87chevytrucks.com/techinfo/TBI_rebuild/TBI-16.jpg)
This is my TBI that was having similar issues where it would not run without giving it gas the regulator spring was broken in mutiple places. (I rebuilt it here: http://forum.73-87chevytrucks.com/smforum/index.php?topic=24770.0 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=24770.0))
The whole troubleshooting thread is here: http://forum.73-87chevytrucks.com/smforum/index.php?topic=3984 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=3984)
I also use this for scanning most TBI's http://www.winaldl.joby.se/ (http://www.winaldl.joby.se/)
Again Verify Fuel pressure first and report.
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Thanks for all the support guys!
Well, looks like I'm running 5 PSI after the (new) fuel filter. Started to uncover the tank switching valve assembly. Notices there is one pink wire showing voltage.
I was under the impression that the tank switch on the dash was a simple SPDT unit. Au Contraire mon frere!
I do notice that when I'm keeping it running and I select the right hand tank, the engine dies as though I cut power to the left hand tank pump.
So, prior to dropping the LH tank, I want to get the tank switch to operate, mainly to see if the RH pump works.
BTW, Where are the pumps fused? All my fuses are good, there are none listed as 'fuel system', only ECM 1 & 2.
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ECM B protects the fuel pump circuit. IGN Protects the fuel gauge circuit. Don't go down a rabbit hole. Validate fuel pressure with BOTH tanks and make sure there is gas in both tanks.
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Thanks VZ, good advice.
Need to verify tank switching valve actually works.
Are there secondary fuses at the ECM B location?
Finally, do the pumps have constant B+? If not I would suppose they are switched at ECM B? Would that be a signal from the tank selector switch?
There is no B+ at the tank switch inside the cab.
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Okay, did some digging into some of VZ's old rants and came up with this:
Fuel Pump Relay (FPR) gets signal from ECM B fuse.
ECM gets signal from oil pressure switch, then signals FPR to energize coil, sending voltage to the Tank Selector Switch TSS
TSS sends voltage to each respective Fuel Pump AND signals motor/relay within Fuel Tank Selector Valve FTSV to move to correct tank.
The B+ I measured on the pink wire at the FTSV is from the ING fuse and signals the Sending Units from the Fuel Module, ergo the weak voltage.
Starting to think the problems are ground related.
Thanks for the roadmap VZ!
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The oil pressure switch is a backup to the fuel pump relay. A better description is here http://forum.73-87chevytrucks.com/smforum/index.php?topic=29825.30
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So Close...Thanks man!
This is the diagram I studied this morning, but the link you sent has much more relevant info.
I'll conduct the test(s) and see where the path takes me.
So, with the truck off, I should be able to apply B+ to the 490 RED wire going into pin C of the relay, and going through the tank selector switch, it should energize each pump respectively. Yes?
Where is the location of the test terminal? I'll look but it didn't jump out at me.
Also if I energize the D pin on the FPR I should hear/feel the relay close.
Thank again buddy!
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The pigtail is hanging off of the relay. Yes
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So I learned a few things today.
The ECM gives a two second signal to the relay, but after that there is no power going to the pumps or tank switch.
I wired the pump test connector directly to B+ and heard good things, like the left pump, and the tank switching valve.
Right pump no so much, I hear a faint noise, gurgling out of the fill pipe, NO pressure.
Left pump much more vigorous out of the fill pipe, sounding like the gas was circulating inside. Still 5 psi.
So electrically she is good, the ECM, tank selector switch, and tank selector valve are working.
Q: has anyone seen things come loose in the tank, where something breaks and it circulates thus dropping pressure? It really sounds strong.
Or maybe the internal filter is clogged. Good chance of that, during muh covid some tweakers cut the elbow hose that drops into the neck on top of the tank and siphoned it out. Probably tweaker dust is clogging it.
In any event, looks like I have to drop it...or both at some point in time.
Thanks again for all your help. I'll keep you posted ::)
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If you have been running E10 (ethanol gas) in it it will disolve the hose between the pump and the pickup tube. This is especially true if it has been sitting. I highly recommend replacing that hose with a submersible EFI E85 safe hose when replacing it IF that is your issue.
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Well Captain, that makes the most sense, since the pump is at the bottom of the tank, and the rubber hose connects the hard line. I hear what sound like circulation, which is probably spraying out of the rubber hose, and accounts for such low pressure.
I found a inline fuel pump from a Benz I had, it measures 50 psi full throttle. Thinking about locating it post fuel filter where hard line converts to rubber.
I'll keep you posted, and THANKS!
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She Lives!!! ;D ;D ;D
So I placed a pump inline by extending the rubber fuel line, and back then back to the TBI.
It works on both tanks.
Haven't heard her run for months!!!
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Good to hear that she's up and running! Cheers! :D
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Thanks!
Took her up to the car wash for a long overdue scrubbing.
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So I took her for some new sneakers on the rear dually's, and she started to choke up, lost power and threw code.
44, so I guess she's running lean? I already changed the 02 sensor.
Looking on ebay/amazon for a OBD1 right now. >:(
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Why did you use that fuel pump? You need to push the fuel not pull it and you need a steady 13 psi
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Well I didn't see this pump as a permanent fix. I will get the tank pumps replaced.
It would seem that under load the volume required is impeded by the hose decay between the tank pump and the pick up tube.
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Another theory-
Probably had 2-3 gallons, so with the level so low, the secondary pump was most likely drawing air into the damaged hose.
Primary only delivers 5 psi at the moment, so we had a diluted mixture of air and gas.
I bought some 'catcleaner' additive, added 2 gallons, drove for 12 miles, mixed fwy and surface, avg 45-65 mph.
She cleared up nicely after about 5 miles. Filled her up with premium, now let's see if she passes smog... ::)
Oh, and the 32.00 OBD1 doesn't do anything but short 1+2, just like my paper clip!!! >:(
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Right, a code reader is not a scan tool so don't waste your money on one. "Premium" will not help with emissions. In fact it may cause your HC's to increase.
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So VZ, is there a OBD1 that actually scans? Or do we just have to count the blinky lights?
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I have an INNOVA Scan Tool 5610 and it does very well on my vehicles made in the 2000s, as for 80s and 90s vehicles there may be additional attachments that can be purchased. It is used with my phone and does a lot. It will break down codes and helps to troubleshoot problems, has many features. You can look it up on line. There are others good ones as well I am sure.
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Here's an old auto x-ray on eBay for under $100 bucks! GM Ford, Chrysler OBDI and OBD2
https://www.ebay.com/itm/155526360331?hash=item243617ed0b:g:dpYAAOSwxsBkSs~G&amdata=enc%3AAQAIAAAA4L%2F1vG0o7352evzDnsbYRqFP477mrtHD8BNgp74qLWyKs3oHwea0n82wmk4Z6bfJd6RFL1v6Hp0fFXX0SArm9kTBRS%2B12TcP%2BFPZr%2BB1bqZPd4Xf%2BvhLLy40DA0XDqgvQjer7Q7FfzA5ayIy8tN3edcvxRAdVhqDgviic7Rrr9FQyaPLg2Elk5eSf%2Fn6i9iiIaNlXYcJMJAmervC4RgxAkvVqN%2BDuLQq1VgorepAONyR5wAzeMhFixzlYwnifAktWGKgfS1EQ4hI0zXsuE%2FAOxkhAZL%2FyEMPOHdhIu02qX%2Fz%7Ctkp%3ABk9SR8bl9vyJYg
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I have read the OTC 2000 works for the primitive diagnostics available on OBD1. Here is a set on Ebay that includes GM TBI brainbox.
https://www.ebay.com/itm/233795455727?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D20220706173935%26meid%3D79c381f765914eb0a9180413dab6d644%26pid%3D101526%26rk%3D1%26rkt%3D1%26mehot%3Dnone%26itm%3D233795455727%26pmt%3D0%26noa%3D1%26pg%3D2380057%26algv%3DRecentlyViewedItemsV2Mobile%26brand%3DOTC&_trksid=p2380057.c101526.m146925&_trkparms=pageci%3A61b5d1e3-fa95-11ed-b904-1649b703dc1e%7Cparentrq%3A505dc0541880aa7145e3f636fffcd937%7Ciid%3A1
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Thx guys! Will let you know what happens!