73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Electrical => Topic started by: Jheald65 on October 25, 2017, 05:43:35 PM
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Hi -
I looking for some information that maybe listed somewhere on the site but I haven’t found it yet .. so I don’t mind if I’m referred out to an existing thread ...
My son was driving the truck the other day when it started to stumble off the line from a stop light , under normal driving.. then it ran ok for a couple hundred feet then died .
We had it towed home .
I’ll summarize the situation:
Truck will crank but not start
Have spark to the plugs per visual
Sprayed starting fluid into the throttle body - no change , engine doesn’t “try” to start at all .
Test of the 2 pin fuel pump plug at the drivers side tank is 6.5 v I’ve not tested the passenger side fuel pump yet to see if there is less than 12 v
Fuel pump relay plug , not the relay , was tested and have 12 v to terminal A , but when key is turned on , no 12v to terminal D , only 3.4 v
Full battery
No fuses blown
Fuel pump tested direct 12 v runs good
Pump removed and filter screen was brittle and broken .
I’ve not tested the ICM , passenger side fuel tank pump , or transfer valve ..any help or advice is totally appreciated
1987 1/2 ton Silverado
305 cu. in
TBI
700R4
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There may be an issue with the pumps wiring, but it should've done something when you sprayed it with starting fluid. That leads me to believe there's a spark problem. You can also check if the pump is working by undoing the fuel line into the motor and running it into a bottle. Turn the ignition on and see if she pumps.
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something doesnt seam right these engines dont really require a whole lot to run. fuel, air/compression and heat. if you can spray fuel in the TB and you know you have spark then air/compression would be whats missing.
start here
http://forum.73-87chevytrucks.com/smforum/index.php?topic=24743.0
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460,000 original miles? Does the engine share that mileage? Has the timing chain ever been serviced? Go ahead with the diagnostics presented in the linked guide, but add to that, "check the timing chain." To check timing chain play read reply #4 in Re: 86 C10 Loping (http://forum.73-87chevytrucks.com/smforum/index.php?topic=27593.msg229607#msg229607).
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Before you pull the seat out of the truck while standing on your head,
SES light come on with bulb check? Adequate spark from the ignition coil? Injector pulse?
Follow engine cranks but does not run diagnostic flow chart A3
CHART A-3 - ENGINE CRANKS BUT WILL NOT RUN
Circuit Description :
This chart assumes that battery condition and engine cranking speed are OK, and there is adequate fuel in the tank. This chart should be used on engines using the Model 220 throttle body.
Test Description : Numbers below refer to circled numbers on the diagnostic chart.
A "Service Engine Soon" light "ON" is a basic test to determine if there is a 12 volt supply and ignition 12 volts to ECM. No ALDL may be due to an ECM problem and CHART A-2 will diagnose the ECM. If TPS is over 2.5 volts the engine may be in the clear flood mode which will cause starting problems. If coolant sensor is below -30~C, the ECM will provide fuel for this extremely cold temperature which will severely flood the engine.
Voltage at the spark plug is checked using Spark Tester tool ST 125 (J26792) or equivalent. No spark indicates a basic ignition problem.
While cranking engine there should be no fuel spray with injectors disconnected. Replace an injector if it sprays fuel or drips like a leaking water faucet.
Use an injector test light like BT8320, or equivalent, to test each injector circuit. A blinking light indicates the ECM is controlling the injectors.
This test will determine if there is fuel pressure at the injectors and that the injectors are operating.
Diagnostic Aids :
If no trouble is found in the fuel pump circuit or ignition system and the cause of a "Engine Cranks But Will Not Run" has not been found, check for:
Fouled spark plugs
EGR valve stuck open
Low fuel pressure. See CHART A-6.
Water or foreign material in the fuel system.
A grounded CKT 423 (EST) may cause a "No Start" or a "Start then Stall" condition.
Basic engine problem.
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Could also try running a jumper wire from the battery to the fuel pump
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Thanks for all the input , unfortunately I’m at work for another day so I won’t be able to test anything til then , thank you for the information .on diagnostics .. I’m going to start over at step one in case I’ve overlooked something and will update on my findings .. but yes to answer the question ,the truck is completely original, my uncle bought it in 87 new from the dealer . Drivetrain is all original, and has never broke down before .... aside from water pump s and alternators this truck has never left me stranded....
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So , have eliminated the fuel pump relay .
I do have :
12 v at the battery , 10.3while cranking
12 v at the fuel pump relay , with the priming lead for the pump coming on for 2-3 seconds then off .
12 v at the injectors 9.7 while cranking
Still 6.5 v at the fuel pump.
I worked backwards from the fuel pump to the tank selector valve and was not able to pull any power with my test light at Any of the pins on the plug ?
And no power up in the cab at the tank selecto switch on the dash either .. I’m getting ready to go over the schematic on the wiring now
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have you tested the fuel tank switch yet or replaced it? not the valve but inside of the cab theyre known to get all gunked up and work sometimes and not others
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also did you jump the red jumper wire on the relay and try to start it that way?
for the switch
http://forum.73-87chevytrucks.com/smforum/index.php?topic=6537.0
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heres my little run in with the tbi. vile, capt and BD really helped out with diagrams and trouble shooting
http://forum.73-87chevytrucks.com/smforum/index.php?topic=29825.0
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SES light come on with bulb check? Adequate spark from the ignition coil? Injector pulse?
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so , I jumped the 12 constant from the electrical connection of the fuel pump relay plug (orange wire) to the tan /white. Wire of the plug . Now I have 12 v power at the tank selector switch in the cab , 12 v and power to the fuel pump on the drivers side ... and the fuel pump comes on nice and strong but like I said , it’s the constant power ... when jumped , the pump is always on . And that’s where I left off it got to dark ...bypassed the relay itself
I did jump 12v wire from the pos terminal of the battery , to the 3 in pigtail of the fuel pump relay test wire ... nothing happens
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Yes , SES light is on , there is spark at the plug , but unknown if injector pulse , as the pump is out if the tank , and the passenger side is empty due to a leak in the tank from year ago .
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What does the fuel pressure module under the dash look like ? I see the diagram but can’t tell if what I see is the same thing ...
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Ok , so I worked til it got dark and had a rather odd finding, long story short , I put the old fuel pump relay back in , now .. when the keys turned on , the right pump comes on and cycles for 2-3 sec, and shuts off ... turn the key off , switch the tank selector switch , turn the key , the other pump does the same ...... just like it’s supposed to .....?...... I changed nothing .... but I put gas in the throttle body and tried to fire it up but it won’t fire ,... done for the day , battery is in the charger, I’ll tomorrow...
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Honestly I think you're going down the wrong path. If it was a fuel related issue it should have started on starting fluid
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I agree
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You've verified that the pump is putting 12 psi of gas at the TBI with a pressure gauge ?
Purchase a noid light and verify that the computer is telling the injectors to squirt
https://shop.advanceautoparts.com/p/otc-gm-tbi-noid-light-otc7187/17632201-p?c3ch=PLA&c3nid=17632201-P&c3apidt=27667980540&gclid=EAIaIQobChMIsrX2ou-e1wIVSGV-Ch2-vQncEAQYASABEgLtGvD_BwE&gclsrc=aw.ds
Timing chain ever replaced ?
If the timing chain gets worn and jumps a tooth or two it will spin over but won't run
An engine needs compression , proper amount of fuel , and spark at the right time
Put a fuel pressure gauge at the TBI , to verify that the pump is working right
Put a noid light on the TBI
And check the compression with a compression test gauge
Post up the numbers you find with the psi and compression
Do NOT use a normal test light at the injectors
The injectors always have 12 Volts and the computer grounds them to make em work
You can buy a LED test light that's safe for using with computes but that usually doesn't work with injectors since the electricity pulses so fast
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I wondered how long it would take to come back around to this. Earlier, you claimed to have spark and fuel. With 460k miles, do this before investing any more time or money in other tests... How to Evaluate Timing Chain Condition (http://forum.73-87chevytrucks.com/smforum/index.php?topic=35820.msg302304#msg302304). Scroll down to "Checking the chain." If valve timing is far off, the engine will play dead. Everything else is subordinate. Under the circumstances, only after you verify valve timing should you proceed with other tests. 8)
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You know be after you posted the idea of the timing chain I was pretty sure that would solve the problem. But for some reason I forgot about it and was helping trouble shooting a fuel issue which I was sure from the beginning wasn't even the issue since it didn't run on starting fluid
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I walked into a very remote, long abandoned mine out in the desert early one Summer, being very attentive to watch for aging dynamite, rattlesnakes, rotted shoring, loose ceiling blocks, camouflaged raises and other fatal surprises. It was very bright outside, shortly after noon. I was studying the mineralized veins oriented along a fault which the drift followed. After about fifteen minutes I became troubled, because my eyes simply wouldn't adjust to the low light. Even using a bright flood, I struggled to see and became really agitated as I began to worry I was going blind. Eventually I gave up and exited the mine. As I walked outside I realized I was still wearing my dark glasses. They were quietly riding the bridge of my nose and I hadn't a clue. So, I know exactly what you mean....
Of course, there's no assurance that valve timing is the culprit. It needs to be checked. But, if it isn't the cause, it oughta be. :D Haha!
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just like my quote from S.H.
When you have eliminated the impossible, whatever remains, however improbable, must be the truth ~Sherlock Holmes
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I used to have a truck that wore out the timing chain and would jump time about every 10-12,000 miles , or about once a year at the rate I drove it
I got pretty good at changing it .
I was penniless at the time , couldn't afford a new engine ,
The crank bearings were so worn out you could see the crank pulley move when you pushed in the clutch
And you could see the oil pressure spike on the gauge when you took you foot off the gas suddenly and changed gears
Because the crank would move up in the block
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Was her name Lucy? :D
Crank no start simple checks: spark, fuel, ignition timing, mechanical timing, compression.
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Thanks for all the advice.. I’ve been out of the state , and coupled with bad weather have detoured the assessment process ... I’ll be back on it in a couple days ... and will share my findings
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Put a compression tester on 'er! The suspense is killing me..
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The only operation I had time to do today was to check the elongation of the chain as specified in the link ...
I have degree marks on the timing tab , and when rotated counter clockwise , I get a solid 8 degrees of movement before the distributor rotor slightly moves..
I repeated the test 2 more times and got the same results
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You are going about this all wrong. Follow these recommendations previously mentioned:
Crank no start simple checks: spark, fuel, ignition timing, mechanical timing, compression.
As in validate consistent spark from the coil wire and at more than one plug wire. Validate that you have injector pulse. If all is good, validate fuel pressure. If good, check compression. That's all you need to do to determine where your problem lies.
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Thanks for all the help
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Just an update....
Removed all the plug wires from the cap and found rust and oxidation to the inside of the plug boots and on the posts of some of the cap terminals, some of the plug boots are split on the back sides
The inside of the cap shows signs of age and wear, and the rotor was very dirty ...
a lot of play in the shaft of the distributor and general neglect . Any recommendations on a new distributor
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Replace plugs, wires, cap and rotor. I wouldn't worry about the distributor itself
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If the distributor is in the condition you say then replace it.
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If you have a timing light pulling the distributor ain't no thing.
I was having crank/no start on my 87-tbi 454 and it ended up being the pick up coil. I had to pull the distributor, I took the cap off and made some marks on the base of the distributor to reference it to the engine and also another mark where the rotor was when installed and were the rotor was after I pulled it out. The second mark is so I didn't end up a tooth off on timing. I went ahead and rebuilt it all with a new cap and rotor and ICM.
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Yea that’s my plan , I’ll re build the distributor , the pick up wires are cracked and the plug is broken... it’s not a choice at this point , and to go along with that I’ve got new cap ,rotor , wires , plugs . After turkey day I’ll. Get it back together..
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Anyone happen to know a place to get a distributor shaft assembly for this 87 305 ?
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Just get a new distributor, they're relatively inexpensive if you buy online. I see them on eBay for around $40 bucks, auto parts stores around $90 bucks. If the shaft is damaged, the unit should be replaced.
Click Here (https://www.ebay.com/itm/Cadillac-Pontiac-Chevy-GMC-Pickup-SUV-Van-Ignition-Distributor-Assembly-19179575/302530743001?fits=Year%3A1987%7CMake%3AChevrolet%7CModel%3AV10%7CSubmodel%3ASilverado%7CEngine+-+Liter_Display%3A5.0L%7CTrim%3ASilverado+Standard+Cab+Pickup+2-Door%7CEngine%3A5.0L+305Cu.+In.+V8+GAS+OHV+Naturally+Aspirated&epid=2278890240&hash=item46703ccad9:g:VuUAAOSwR1FZ5Ldq&vxp=mtr)
AutoZone BDLG-GM04
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(http://media2.giphy.com/media/SVL5Dws0bOSgE/giphy.gif)
Just get a new distributor, they're relatively inexpensive if you buy online. I see them on eBay for around $40 bucks, auto parts stores around $90 bucks. If the shaft is damaged, the unit should be replaced.
Click Here (https://www.ebay.com/itm/Cadillac-Pontiac-Chevy-GMC-Pickup-SUV-Van-Ignition-Distributor-Assembly-19179575/302530743001?fits=Year%3A1987%7CMake%3AChevrolet%7CModel%3AV10%7CSubmodel%3ASilverado%7CEngine+-+Liter_Display%3A5.0L%7CTrim%3ASilverado+Standard+Cab+Pickup+2-Door%7CEngine%3A5.0L+305Cu.+In.+V8+GAS+OHV+Naturally+Aspirated&epid=2278890240&hash=item46703ccad9:g:VuUAAOSwR1FZ5Ldq&vxp=mtr)
AutoZone BDLG-GM04
(http://www.dieselplace.com/forum/images/smilies/icon_nailhead.gif)
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I already have one on order , but will be rebuilding the other one ... not a big fan of the cheap replacement parts , I don’t mind the cost difference for added piece of mind ... once I get it all back together I’ll update ... thanks guys
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sometimes those cheap replacement parts will outlast a name brand that comes from the same factory. theres a few of us that run the cheap distributors off ebay because its more cost effective to replace it all and no one that i know of has ever came back and said the new distributor is bad already
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Just an update , swapped out the distributor and got it running again . Thanks for all the help