96 chevy fuel surges

[planeguy140]

I have a 96 chevy 1 ton pick-up that is acting up. Twice recently I start it up and the throttle goes full open and the truck blows an incredible amount of smoke. Ysterday after this happened it settled down and I attempted to drive it. The throttle started surging from 700 rpm up to 3000 rpm and then back down. I installed a new fuel filter, checked the fuel, and it still did it. After leaving it overnight, it started up fine today. This is the second time this has happened, and the next day it runs fine. Please help with any suggestions. Thanks

[65TD]

Got some error codes?

[planeguy140]

I did not see a check engine light to display any codes, or I possibly missed that it was on. Again, It started just fine today so there are no lights. I will make it a point to look if this happens again.

[65TD]

Make sure the SES light works when you first turn the key on.

[planeguy140]

I do know the SES light does work when first started up. I just did not see it lite when the engine started to cycle. The engine would surge up and down, blowing huge amounts of smoke as it surged up to 3000 rpm. Today after starting, the engine ran fine, with no smoke or cycling.

[Mark Rinker]

I would check for any stored codes - even if the SES light is off. My guesses:

1) Was any underhood maintenance done prior to the runaway engine? Especially any that could have introduced petroleum fuel vapors to the air intake. Diesels have been known to runaway from cleaning fluid vapors off the shop floor where they are parked. Were any such fumes in the vicinity during startup? Also, starting fluids (ether) is a big no-no for these engines and can cause similar behavior.

2) Throttle. Its not common, but a short or failure of the electronic 'fly by wire' throttle assembly could cause this. Check and clean connectors at the throttle. There is a 'Service Throttle' dash indicator. Has it illuminated?

3) Bad or loose connections at the ECM. Again, this scenario isn't common, but a bad connection or loose ground can cause lots of odd problems. Something is adding LOTS of fuel to your engine, without you requesting it! The ECM is behind the glovebox liner.

4) Bad injection pump / FSD. Again, not common, but certainly involved if your engine 'ghost' is turning up the diesel fuel unexpectedly...


Pull the codes and get back to us. Good luck - be careful!

[Bnave95]

Had a crank sensor acting in the same way before SES light. This will probley act up again,when?
Needed to replace crank sensor. Some go bad and other don't

[65TD]

Is the IP original? How many miles on it?

Any lubrication added to fuel on a regular basis?

The problem your having is a common thing with IP failure.

Might look at the IP and see what model it is and what color the tag is on it.

[planeguy140]

Thanks for all the info and suggestions. I will find a way to check for any stored codes later this week. As far as I know, It has not been exposed to any petroleum vapors. I have had no work done on it recently. I will take a look at the IP.....I'm hoping that's not it. Thanks again.