1989 chevy c2500 start stop scenario

ej1619

Full Member
Joined
Oct 25, 2009
Messages
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Make
Chevy
Model
C1500
Year
1989
Miles
240ish-k
Engine
5.0
Ok guys and gals, this is about my dad's truck. It's a 1989 chevy 1500 2wd with the wonderful 5.0. Truck has just under 250k om the clock. So to the issue, truck starts and idles fine, no misfire, no skipping, runs slick as a whistle until it gets good and warm. Daddy said he fired it drove just over a mile from his house and it started sputtering. Has a new fuel pump, as parts house pumps are as good as pisisng up a rope(lol). He said it did this before when he first bought it(used in 95) the dealer fixed it under the warranty they included in the sale price. I know this truck well, he's taken excellent care of it over years and never any serious problems other than this irritating issue. He did say it has started to smoke a little from sitting, he refuses to drive it to avoid a wrecker bill. Pretty confident that it's valve stem seals being it's the blue/grey oil smoke color.

Any thoughts on what would cause it to start acting up once it gets hot. He said let it cool back down about an hour and she'll fire back up and run just fine until it gets to normal operating. Then it runs like t-total trash until it shuts off. Thanks in advance
 

billr

wrench
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This has TBI? How about the ignition; I expect it has a dizzy, but is advance by both mechanical fly-weights and a vacuum can?

Check all the basics, spark timing . compression, vacuum, and fuel pressure. Check the ECT, MAP, and TP sensors. ou probably won't have an scanner that will show live data for this old OBD1 beast, but you can check those three sensors with just an electrical multimeter.

Block off the EGR valve and disconnect the knock-sensor, see what effect that has. Check exhaust back-pressure or run it for some tests with an open exhaust.

Does it smoke all the time? Check the PCV valve, or disable it too.

Having it run poorly only when hot makes the ECT sensor or EGR system most likely.
 

ej1619

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Thanks Bill, I will convey the information. I'm not hands on living half a day away. He would take to a shop, unfortunately there are few reliable and even fewer shops that work on anything older than a 96 in his area the ones that do are so expensive he could buy a newer truck for the repairing diagnostic charge. Literally quoted him $1300 to diag plus any repairs.

In regards to smoking, he said it smokes pretty much until it starts to warm up. Once it does smoking subsidies for the most part.
 

billr

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So... it smokes but runs fine until it is warmed-up, then it stops smoking but runs poorly, correct?

That still doesn't sound like a problem with the valve guides. Piston/rings, PCV, or a leaking head/manifold gasket. The easiest to eliminate is the PCV, and if compression is low have him do it both dry and wet. A "block test", using the dye in coolant may show a head gasket issue. And the vacuum gauge may show a problem with the intake manifold gasket.

I suggest you encourage the owner to join into this thread. You can still participate, of course, but transferring info "3rd hand" is always subject to some confusion or miscommunication.
 
Last edited:

grcauto

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Ok guys and gals, this is about my dad's truck. It's a 1989 chevy 1500 2wd with the wonderful 5.0. Truck has just under 250k om the clock. So to the issue, truck starts and idles fine, no misfire, no skipping, runs slick as a whistle until it gets good and warm. Daddy said he fired it drove just over a mile from his house and it started sputtering. Has a new fuel pump, as parts house pumps are as good as pisisng up a rope(lol). He said it did this before when he first bought it(used in 95) the dealer fixed it under the warranty they included in the sale price. I know this truck well, he's taken excellent care of it over years and never any serious problems other than this irritating issue. He did say it has started to smoke a little from sitting, he refuses to drive it to avoid a wrecker bill. Pretty confident that it's valve stem seals being it's the blue/grey oil smoke color.

Any thoughts on what would cause it to start acting up once it gets hot. He said let it cool back down about an hour and she'll fire back up and run just fine until it gets to normal operating. Then it runs like t-total trash until it shuts off. Thanks in advance
I'd be looking at the temp senders. ECT is the most critical. If the sensor is failing hot it could be shorted (full hot) to open (-40)
Does it run rich when it happens?
 

ej1619

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Oct 25, 2009
Messages
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So... it smokes but runs fine until it is warmed-up, then it stops smoking but runs poorly, correct?

That still doesn't sound like a problem with the valve guides. Piston/rings, PCV, or a leaking head/manifold gasket. The easiest to eliminate is the PCV, and if compression is low have him do it both dry and wet. A "block test", using the dye in coolant may show a head gasket issue. And the vacuum gauge may show a problem with the intake manifold gasket.

I suggest you encourage the owner to join into this thread. You can still participate, of course, but transferring info "3rd hand" is always subject to some confusion or miscommunication.
I've told him unfortunately my old man is 74 and cantankerous as an old big block. He said he'll check what you suggested. I've sent him a chiltons manual for the ol girl so he can follow test procedures.
 

ej1619

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I'd be looking at the temp senders. ECT is the most critical. If the sensor is failing hot it could be shorted (full hot) to open (-40)
Does it run rich when it happens?
I've mentioned that to him, he recalled that when he first bought the truck back in 94 he had ti take it back to the dealer. Said if he recalls correctly that's what they did replace the sensors.
 

big al

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Aug 27, 2007
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I am with GRC Auto. I had a 94 Suburban that did this same thing. Replaced the ECT sensors and I was back in business' and running good again. When it got warm it would fail and run pig rich. When cold it ran good.
 
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