1999 GMC Suburban Intermittent no start, sluggish when warm

1999GMC454

MEMBER
1999 GMC SUBURBAN
V8
4WD
AUTOMATIC
143,000 MILES

1999 GMC Suburban 7.4 454 that every few months will no start. Wait about 10 minutes it fires right up. Also, the passlock light is blinking on the dash. When the truck is warm after coming out of a store the engine fires but seems like not a good spark. Have had a few issues where you can smell strong gas out of the tailpipe. Engine seems to lack power when it is warm but I cannot confirm that it is just a feeling.

I have read several ideas to fix this but not one concrete answer. Some say passlock module others say the brain behind the instrument cluster.

The fuel pump has been replaced twice and the fuel pressure regulator once. Has new plugs and wires. Code reader comes up with no codes.

Has anyone been able to track this issue down to something?

4 Replies

JDL

MECHANIC
16,098 POSTS

Hi, how long since a tune-up? When the problem occurs, have a helper it, while you visually check for spark at the plugs, if you have spark everywhere, use a gage and check fuel pressure. Around here some of the national brand autostores used to loan out a fuel pressure gage. I haven't looked at your security info, passlock is usually injector disable, got nothing to do with spark.

To check for spark at the plugs, if there is a plug wire, just take it loose, stick known good plug or spark tester in the boot, ground metal part of plug/tester to metal part of engine, watch for spark.

If you have the spider fuel system, they are known for problems.

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Sunday, March 28th, 2010 AT 2:59 PM

1999GMC454

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3 POSTS

Awesome information. I have never heard of the spider system being an issue in my treak across the internet looking for answers. Makes a lot of sense with the intermittent issues I have had.

Does GM have an upgraded system or should I look aftermarket? Is it a design issue or just something that goes bad.

Fuel pressure is perfect according to my mechanic and the plugs and wires are new.

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Sunday, March 28th, 2010 AT 5:55 PM

JDL

MECHANIC
16,098 POSTS

The fuel poppets may need cleaning, if the fuel system, is the issue? The cleaning procedure is a shop procedure. I don't know if injector cleaner in the gas tank will help?

They do have a conversion kit for that system, converts to mfi. You need to be sure of the actual problem.

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Monday, March 29th, 2010 AT 7:54 AM

1999GMC454

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3 POSTS

I agree about needing to be sure of the problem. That is the biggest issue I have right now. No codes and an intermittent problem. All I have to go on is symptoms. Unfortunately, guessing gets expensive.

I can imagine an injector leaking a small amount of fuel which floods the engine and I get that brief no start and the passlock system blinking light and then 10 minutes latter it fires up without issue.

Thanks for your time and suggestions to my problem.

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Monday, March 29th, 2010 AT 8:55 AM