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73-87 Chevy _ GMC Trucks => Members Rides => Topic started by: 1980K20 on August 25, 2022, 09:37:19 PM
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Ok, starting over with the startup note. I meandered about on this, but crossing fingers have a handle on it.
1980 chevy, '91 SBC 350 block with mild roller CAM, Vortec heads, Holley Sniper EFI with fuel pump in the gas tank. Transmission TH-350 with NP205 transfer case. Everything was rebuilt 600 miles ago.
After the first 100 mile drive including nice highway speeds, I filled her up with gas and as I drove home, and it was then driving awful. To be fair, it could have begun to act poorly before I got gas, nice even roads to the station so no hitting the gas hard. Symptoms:
- Truck shook and shuttered when you hit the gas anything but very light tap
- Struggled very hard going up a steep hill into the neighborhood, 20 MPH was it.
- Wouldn't downshift
- Idled fine, revving up in park sounded just fine. Problem only happens when in gear.
- Hold the brake, step on the gas, feels like it wants to go, let go of the brake, not even enough power to make the tires spin
After initial investigation, discovered low on transmission fluid. Being in a glass half-empty mood, assumed that i just trashed the transmission. Naaaah, it's just fine. No brunt smelling fluid. Added fluid and it runs just fine. (I will get it changed in November when it's in the shop). I drove around a bunch running experiments with the following results...
- Occasional backfire, sounds like thru exhaust, when you stomp on it
- When it's cold, stomp on it, backfires and stalls
- People comment that it smells rich
- Missing under load
Read on the internet that many times missing under load is electrical. Discovered the plugs unevenly carboned. #7 is the worst, completely black. #3 was clear as can be. Must be electrical, right? Put in some new plugs, no change. Checked the cap, everything looked fine, but i accidently broke a piece off the cap when trying to get that back hook unhooked, so on went a new cap, no change.
It was suggested that perhaps the O2 sensor went bad, is reading lean, and dumping fuel. Did some reading on the internet which says that can be a problem. Discovered a bad exhaust header outlet gasket that had failed in front of the O2 sensor. New gasket, new O2 sensor. Ran better and different, but still no power. Maybe the old O2 sensor is still good and slightly better running was due to the new gasket.
Took it to a local shop specializes in setting up carbs and efi, he discovered that the tables were all whacked given the problem with the gasket. He fixed it all up, spent a lot of time cleaning things up, fixed some things. Dyno reading much, much smoother than previously. But it only had 195 lbs-ft torque. Something really off. One run had the lbs-ft 207, but then back to 195. Mystery. Engine builder dyno'ed it at 400 lbs-ft. Guy says you lose a good 30% through the drivetrain, which would make my reading around 250, still far off. Found throttle didn't go to max, cause of kickdown issue. Of note: the missing still happened, but it was an interaction with the EFI and vacuum advance. Removed the vacuum advance and missing disappeared. Timing set to 16 initial, 36 max. Guy suggested a fresh set of plugs. New plugs, still runs poorly. #7 carboned like crazy and wet too! Gee, they've all got some wetness to it. I don't think it's oil.
Called the engine builder. Out of business. No luck in mudville.
More reading on the internet. The internal fuel regulator can fail on Holley Sniper EFI. Usually goes from the 58.5 psi setting to 100 psi. Ran a test, mine was around 85, shaking 82-87. Now, new fuel regulator on order.
Oh yeah, aftermarket parking brake won't stay on anymore. Can an O2 sensor cause that? :-) This is certainly the journey of fix the startup issues. It was a ground up restoration, I'm learning along the way, fixing what needs to be fixed. As you can tell, there are a lot of little things being corrected along the way.
It's another week to get the part. Whew!
What other suggestions do you all have?
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If you are talking about the vacuum modulator, it should be connected to manifold vacuum, not ported vacuum.
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If you are talking about the vacuum modulator, it should be connected to manifold vacuum, not ported vacuum.
Alright, I’ll check it. I’ve read that the wrong connection can cause some sort of trouble.
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Old hot rod trick from 70's, disconnect vacuum to the modulator, shift points are much higher and more firm. No or very low vacuum signals the 350th valve body that the throttle is wide open (floored gas pedal). Made the tires chirp when up-shifting.
It won't hurt your transmission, as it causes full apply pressure to the next gear clutch(s) quicker, less overlap during the gear change. Vacuum line to trans modulator should properly be manifold vacuum only.
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Checked out, was on straight manifold vacuum. Strange, last two times I ran it, idle was super low. Set it up to 850 rpm, purrs nicely.
Working the kinks out I suppose
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Thank goodness, transmission guy says it’s all good.
However engine is the problem. Realize now it’s missing under load, probably the el cheapo spark plugs, one is very fouled.
Stopped by a place, got appointment for tuning. Problems with idle too, Snyper efi , may be bad o2 sensor also.
Whew, not so bad I’m crossing fingers
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Engine issues aside, running that low on trans fluid probably stressed it, with some burning, degradation to the clutch discs.
I would service it with new filter and fluid as a protective measure.
If you keep them clean they last a long time 8)
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Will do Johnny, great suggestion! Appointment in November.
Working on the next problem. Cylinder number 7 isn’t fitting well. New plugs in half to start with, no fix. Put on a new wire, expect it to be the same
1,3,5,7. Yowsers, that’s bad.
(https://uploads.tapatalk-cdn.com/20220906/fdaf2186d44d9e21686ef6053af56daa.jpg)
The idle timing without vacuum was about 18, I dropped it to 14.4. The truck sounds awful when you have the brake on and hit the gas. Sounds fine in idle.
So there’s multiple issues, but what would cause just one plug to completely foul up?
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It appears that cylinder #7 isn't firing at all. Remove and inspect the spark plugs on the even bank. Verify the firing order. Run a wet/dry compression test on all cylinders. Closely inspect the distributor cap for cracks and carbon tracking and the condition of the carbon button. Inspect the rotor for heat stress and perforations through the rotor directly above the distributor shaft. Measure the resistance of the spark plug wires and look closely up inside the wire boots for greenish discoloration and/or black soot. Make sure the ground strap is in place under the coil cover. At any time, did you disassemble the distributor and remove the shaft?
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Running Rich all around, I looked up on line, found exhaust leaks can cause this. Boom, bad header to exhaust gasket, cheap one, just in front of o2 sensor. Will get a new gasket and two plugs to replace the two I’ve horribly fouled.
(https://uploads.tapatalk-cdn.com/20220907/ed68afc06f4358af38616096ce8643c9.jpg)
Here’s the bad exhaust gasket. It was loose and broke apart in my fingers. Lots of carbon.
(https://uploads.tapatalk-cdn.com/20220907/ecbce17fba973184554616e3831891c9.jpg)
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New exhaust collector flange installed, still runs poorly. Checked compression, all good 150-155 wet.
I’ll put in a new cap tomorrow, I broke a little piece of trying to get the hook in place. Ordered a new o2 sensor since that could cause these symptoms.
Found the idle setting was too low causing the servo not to kick in, so at least I fixed two things.
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...At any time, did you disassemble the distributor and remove the shaft?
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...At any time, did you disassemble the distributor and remove the shaft?
Oh no.
I did put on a new cap today. New exhaust collector gasket, but I think the damage is done. New o2 sensor on order.
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Bad o2 sensor! Still doesn’t run like before, but behaved much differently and better. Took her out for a four mile drive, ran 2nd gear to keep the rpm’s up above 3,000 and try to get the efi to start relearning. Ran a bit better when I got home. Now gas gauge says I’m running out. Guzzle, guzzle. Looking forward to getting it running right and seeing where I stand in mpg.
Appointment Saturday at carb connection, should get it straight. I’ll wait until I get there for new plugs.
Thanks again for all the advice!
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Changed title of this, it’s really been a goose chase.
Took the truck to carb connection Saturday. They fixed some things…
1) cleaned up tables from the bad o2 sensor
2) idle timing 16, disconnected vacuum advance since it was fighting the efi and causing some miss
3) added an extension for the accelerator and now throttle is smooth as silk. Also fixed that it was just a touch off from full throttle
4) readjusted kickdown
It ran better but stop no get up and go. New set of plugs, also fouled.
Discovered that intake manifold is a dual plane. He has recent experience with an sbc383 stroker that they got another 40 HP.
Did some more reading on the internet, found a bad regulator can cause this issue. Put pressure gauge on, when 85 psi, not 58.5.
FYI he thinks the 180F thermostat is perfect. He thinks a 195F will get another 0.2-0.3 MPG, not much. Once this is all fixed, will see where it all stands.
Pictures of high pressure, plugs along with number seven from fresh set of plugs if I can get taptatalk to cooperate.
Regulator on order, will update you next week.
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(https://uploads.tapatalk-cdn.com/20220919/287c3af9a8f17ee772a25994c1f66187.jpg)
(https://uploads.tapatalk-cdn.com/20220919/8e2a40e904644b2dba53c1ffe74d4b44.jpg)
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Your edited post makes this thread a mess. You originally posted about your transmission, edited the post to "too much fuel goose chase" and have nothing listed in pinpoint steps to be helped or to help others that might have an issue that you are having. If I read this right, you have a driveability issue going on that originally made you think you had a transmission issue. You mention "carb connection" but you have EFI? Why don't you start over, provide your specs, and what you have going on? What fuel and ignition setup do you have? What issue are you currently having? Describe the symptoms.
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Good suggestion. If I could, I'd just delete the entire thread and start over.
I rewrote the intro thread with the symptoms, experiments, and progression of the debug. Of course, changed subject again.
Mark
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Well the saga continues. The pressure regulator came in early. Same reading around 85. So I thought I’d check the return line, it read 25! 25+59.5=84.5. Hmmm, coincidence?
We’ll gee whiz. I’m done with hope, this is indeed a goose chase. Tomorrow is time for air hose to see if there’s something up with the lines, or just run the return to a gas can.
(https://uploads.tapatalk-cdn.com/20220923/8d1354908ae0e6446f0290dd609bc979.jpg)
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Discovered my return line was kinked in one place. I think the long hot drive softened it and it failed in the loop to allow for installation. Unkinked it and pressure dropped to 2. Dropped the gas tank, created custom stainless bend to prevent the kink. Now pressure is zero, I haven’t tested the intake pressure yet.
Test drive it, runs basically the same. Feels like it’s continually missing. Many times that is electrical, but now who knows?
At least I fixed something today.
Pictures of the kink and the tube I used to make a circular bend.
(https://uploads.tapatalk-cdn.com/20220925/5f6db58b2f39ebd00fa56549192b3aab.jpg)
(https://uploads.tapatalk-cdn.com/20220925/cd608eac80c4e0beb1a565a21cb9f909.jpg)
(https://uploads.tapatalk-cdn.com/20220925/11d0d6907de1b2b3758788b1939562a2.jpg)
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Wondering what your reasoning is on the stop sign shaped loop. Can't you just use a proper length hose? Maybe the fuel is getting dizzy being sent in circles like that, I got a bit dizzy trying to follow thread to getting here at the fuel return from the damaged transmission concerns.
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Hi Geezer,
I thought I had a nice long loop that would have been fine, but it obviously kinked.
Sorry about the meandering thread. You can’t delete and start over.
I checked the pressure on the intake this afternoon, it said 65. Should be lower but maybe it’s my gauge.
Found the big issue at last, I think. At least I know it’s a problem. Learning curve on efi is huge.
One jet on the passenger side isn’t doing anything. I’ve got a dual plane intake, drivers side gets double the fuel, which speaks to many issues.
Pulled the passenger side injectors off. Both electrical fittings looked tight but rear passenger clip broke off easily. Apparently that’s a thing with Holley efi
. Bench tested 12v into the injectors, heard them click. Swapped rear to front, used zip ties to hold both connectors in place, front injector gives nothing. Something with the injector, not electrical.
I’ll get a new injector, put on a new fuel filter just in case there’s some debris in there that got through.
Here’s a picture with the side cover off the efi
(https://uploads.tapatalk-cdn.com/20220926/152b3fc81214f9a8eff111f28e4a1922.jpg)
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Well I gotta say man, she is super clean. Hope you find out what ails her... :'(
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Well I gotta say man, she is super clean. Hope you find out what ails her... :'(
Thanks Johnny!
Will update on Sunday, new injector comes in Saturday.
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Alright, the injector was the final problem. Fixed along the way actual problems (replaced a few other things also but not real problems)
1) Bad exhaust collector gasket in front of o2 sensor. Every seam on the exhaust leaks a little!
2) pinched return hose, probably a foot too short
3) accelerator extender and reset kick down
4) gas filter was 30 micron, not 20.
5) injector clicked but didn’t spit gas
If the injector weren’t bad, I may not have found the other issues.
Plug #7 was previously super fouled. I took out #7 after the repairs, it cleaned up nice. Bottom was before, top is after fix. I had put in fresh plugs
(https://uploads.tapatalk-cdn.com/20221009/8479df2ec1727607aaba098dbdd27c18.jpg)
Got the sniper efi tuned up. Have to work on cold start but it runs well now! Still can’t spin tires, thought that should be easy, apparently not. This is in a wheel Dyno, at the crankshaft is something like 25% more. Timing is still 34, I’ll get to 36 soon.
Max Hp 233 (168 with bad injector)
Max torque 260 lbs-ft
Thanks for your help!
(https://uploads.tapatalk-cdn.com/20221009/f4c5019f07e430210a42b6291d5f610e.jpg)
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:D
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Nice to see you have the problems fixed! Congrats!
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Thanks Shifty and Mike!
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I'm sure you can spin them right after a car wash, ;)
I do it all the time to get my fix 8)
This has been a long thread/journey, Thanks for keeping us in the loop!!