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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: 1987_V10_FARMTRUCK on November 10, 2014, 08:20:20 pm
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Hi All,
I have a 1987 Chevy V10 (305 cu in, TBI, 4-speed manual, LWB, dual tanks) truck that is our prime farm truck. For the past year or more, the has had a bit of a mind of its own as it will all of a sudden die while driving or not start all together. When it cuts out, it acts like it is starved for fuel and if you put your foot into the gas to keep it going, it just sputters and dies. It will start again, but after waiting a while... seemingly longer the wait if it above 90-degrees outside. More recently, the truck will only run with massive pumping of the gas and feathering of the clutch and has absolutely NO power... not even enough power to move the truck in 'low' granny-gear (the feathering scenario only after the truck dies in traffic or in the field).
I am a bit of shade-tree mechanic as you have to be with a farm, so here's a list of the things I have tried and new parts installed but have made no difference:
A) New Bosch fuel pump & screen (I only use the left-side tank as the right side tank never worked in the 11-years owned).
B) New 16-gal tank and rubber lines from sending unit to steel lines.
C) Blown out fuel lines.
D) New fuel filter.
E) New fuel pump relay.
F) New catalytic converter (the truck has a kind whooshing sound when running, so I thought maybe this was bad... but not).
G) New coil (cap and rotor recently).
F) New plugs gapped to 0.35.
G) Rebuilt the TBI with kit.
H) Removed and cleaned the EGR, which was sticky.
I) Truck is getting fuel to the TBI and I want to say that starting fluid doesn't make it start like I thought (hoped) it would.
As of yesterday, the truck is still on jack stands in my shop and wants to start and when it does... it barely catches (with pedal full on or pumped), runs slightly and dies... I could really use some help, as I have tried literally everything that is in my wheelhouse and nothing has made a difference. The good thing is, we love the truck, so the new parts will only make it better once we figure out this little hiccup.
Thanks,
Justin
F)
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After it dies are you getting spark?
If no, try the ignition module in the distributor, or possibly, but less likely the ignition coil.
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I'm with engineer ICM sounds like the problem but check for spark before replacing anyparts
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Holy cow. I just looked up symptoms of a bad ignition module... pretty much all the symptoms I have or have had. Thank you so much, I will be heading to Napa tomorrow after checking for spark and will advise. Stay tuned!
Thanks again!
Justin
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We have a post on here for people that have problems with spark. Its cheaper to buy a whole new distributor off eBay than to guess what the problem could be. Think we found some for $40 with free shipping.
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When you had the throttle body apart did you check the pressure spring, I've had them break before. also have you checked or replaced the throttle position sensor (tps)?
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Thanks for the follow up questions. I thought it had spark as it would catch on occasion, but after reading up on the ICM, it surely has to be the issue (prior conditions and current). I have the TBI slightly disassembled now and everything looks to be in order, negative on the throttle position sensor, but will give it a look while there. The temperature here in CO dropped dramatically (12F by the time I get home from work), so will be picking this back up over the weekend.
Cheers.
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Testing the TPS is really simple.
There are three wires. 12v, ground, and signal.
With the key on, determine which wire is the signal and by back probing the connector to the signal wire, its voltage should vary by opening/closing the throttle. Using a voltmeter to read the values you should get a value that varies between .5v at idle, and 4.5~5v at wide open throttle.
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Okay, I got some time to work on the truck this weekend and pulled out the ICM where I saw the little scrawl of Sharpie written on the old ICM "4/14". I had forgotten that I had changed this earlier in the year... but don't remember putting the grease on the plate and the ICM I pulled was dry. This most likely led to a rapid decline of my ICM overheating as the truck worked for a while after changing. So I installed a NEW ICM with heat dissipating grease and reinstalled the distributor cap. I tried starting the truck, but could not get it to run more than a faint idle with full throttle for a few seconds. It has spark, getting air, so maybe I should look at fuel again? The TBI has fuel and is pressurized, starting fluid makes no difference on running/starting. Ugh. Ideas welcome.
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If everything you say is true then it sounds like your exhaust is plugged.
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any luck 87_v10??
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Check the alternator. If its only putting out voltage in or below 12vdc then it won't be enough to keep the truck running. The old ecms are not very efficient and require optimum voltage to fully operate. A lot Che kthe idle air controller. If its not closing or opening properly the ecm has a hard time metering fuel.
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have you checked what kinda fuel pressure you got?
and look at you injectors when it is runnin one may not be pumping right my 95 has a bad injector that doesn't pump right and has no poewr
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If you are still working on this problem I have seen a couple things cause similar symptoms. I would get a look at the pick up coil in the distributor and the magnet built onto the shaft. If the magnet has cracks it will deliver a weak signal. Beware I have seen some aftermarket distributor cause cold weather starting issues so I would recommend a acdelco.
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If everything you say is true then it sounds like your exhaust is plugged.
You said that you already replaced the catalytic converter, so it should be easy to disconnect the exhaust system from the rear (output) side of it.
See if it starts. Its any easy test that won't cost any $$.
Where you said the truck had a "whooshing" sound to it, I think Vile nailed it.
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i had a similar problem on a tbi 88 i did a swap on. it was the hard plastic vacuum line that goes to the module to the left of the throttle body.