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Gm Tech (Cam)
Gm Tech (Cam), GMC Mechanic
Category: GMC
Satisfied Customers: 1672
Experience:  GM Grand Master Technician 2007. 14 year experience.
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98 vortec 350 wont start once the engine warms up unless you

Customer Question

Hello 98 vortec 350 wont start once the engine warms up unless you hold the pedal to the floor new gm fuel pump new spider injector upgrade new regulator new fuel filter. Help LOL
Submitted: 1 year ago.
Category: GMC
Expert:  Reggie Whiddon replied 1 year ago.

Hello, I'm Reggie thanks for the question, this is going to be fun. Okay 98 3500 with a 5.7. Cranks and runs fine until it warms up, at which point it Will only Start if you hold the pedal to the floor? Once you start it in this manner how does it run will it idle? I hate to hit you with a bunch of questions be patient. With me and we Wil fix this. Are there any codes? Do you have a scantool? Have you checked fuel pressure? Do you have the engine with the flat distributor cap? This is what I'm thinking you say it want start unless u hold pedal to floor, On a modern fuel injection system when you hold the pedal to the floor you disable the fuel injectors, it's called clear flood mode. Which makes me wonder do we have like a coolant temp sensor stuck cold causing a rich condition that you are curing by using clear flood mode?. We know this it cranks only because you used clear flood mode. Can you read live data? If so duplicate the no start and let's look at coolant temp, intake air temp, fuel trims, and gm/s from mass air flow


Expert:  Reggie Whiddon replied 1 year ago.

Where all of those parts you installed in pursuit of this same problem? If so have they had any effect on it?

Customer: replied 1 year ago.
Same problem before I did the installation one started it runs normal and no codes when you start you have to wait a minute for it to idle down or clear the fuel
Expert:  Reggie Whiddon replied 1 year ago.

So it is flooding at restart, do you have fuel pressure gauge? Let's check and eliminate the possibility of an internal leak. Tell me what equipment we have for testing. Scan tool, fuel pressure gauge, voltmeter?

Customer: replied 1 year ago.
Checked the fuel pressure it is good
Expert:  Reggie Whiddon replied 1 year ago.

So you have 60psi with key on, does it hold this pressure. I wasnt so much intereested with the pressure i want to confirm that we are not bleeding off in the engine which is the most common problem with this system

Expert:  Reggie Whiddon replied 1 year ago.

Sir are you still there? I think we can pinpoint the cause of this pretty quick

Expert:  Reggie Whiddon replied 1 year ago.

sir just wanted to check in with you, have you fixed your problem. Just wanted to say, i know it can be frustrating, trying to get something going, heck here it is at christmas, need it running and dont need to spend any money. I will tell you this,, I can help you actually on this type situation i would be hard to beat. For i have built many of these trucks, and was trained by gm. If you want my help and I am here, and I guarantee you we will fix it. If I ask alot of questions at first, please remember i am not there i cant see smell or hear, and I dont know your skillset or your tool arsenal. But i know your truck every square inch of it what size bolt what part number down to the last piece. n

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