fouling plugs

[MX Quad Dad]

I have a 1999 Gmc with a 5.3 I bought from my son. He said the plugs only last about 10,000 miles. he did mostly local driveing so I thought it would be better for me. But, after about 10,000 miles it starts acting-up. I would swear the fuel pump is going out or fuel filter is pluged. I would say it is a bad hesitation, won't take no throtle until it warms-up a little. I should add it is ok on the first start-up in the morning just the start-ups after that. i would say first sign is after making a quick stop (5-10 min.) were it doesn't cool down completely and if I let it go it does it after sitting all day at work. 8 new plugs and it runs great. it doesn't seem to matter which plugs i use cheepos to expensive.

I've dug arround the net a few times but can't find anything

any ideas?

[wistech]

If thats the one with the remote injectors connected with tubes inside the intake manifold its a sure bet the tubes are cracked and leaking fuel . you can buy rebuilt assemblies pretty cheap online. Very common problem. If its a throttle body look at the injectors to be sure both are spraying while its running. and of course spray water on the plug wires at night (to see the sparks) to be sure they are not arcing from cracks.

[quadracer500]

Check the fuel pressure regulator for leaking into the vacum hose.

[wistech]

QUOTE (quadracer500 @ Feb 9 2010, 11:43 AM) <{POST_SNAPBACK}>

Check the fuel pressure regulator for leaking into the vacum hose.

I had a impala with that probelm. it had an intermittant hot stall. When you shut the car off and let it sit for and hour . Fuel would leak into the engine and flood the engine on initial startup causing a stall. if it sat longer like all day it wouldnt occur because the fuel would disperse and evaporate. I found that one easily on the internet and a fuel regulator fixed it .

[cannondale27]

If you could post a pic of the plugs it would sure help.

[MX Quad Dad]

I chucked the old plugs, so will have to wait a while for these to foul. but they looked ok, like plugs with 10,00 miles on them, Fuel pressure regulator is good. and I checked the plug wires with water at knight. not really sure what wistech is talking about as far as tube being cracked. I need to look into that. Truck is getting about 16-17 MPG even when it runs bad. its got about 250K on it and uses less than 1 quart of oil in 5000 miles. My son bought it with about 150K on it and he said it done this since he has had it

Thanks for the help and wisetech if you can describe what you were talking about a little better I,ll check into that

[saltus440]

You are having a problem with the fuel injection spider. The type that came in those trucks from '96-'99 were problematic. They are poppet style injectors that are leaking after the truck has been run and has built fuel pressure. After the truck has been shut off the system is still pressurized and the injectors are leaking into the intake manifold causing it to be hard to start. It starts easily after it has sat all night because all the fuel has had time to evaporate. GM has solved this problem with a revised spider unit that has mini injectors instead of the old poppet style. It comes as a complete spider unit (base, injectors, new regulator). should cost around 300'ish from dealer if I am not mistaken. I can't recall if it comes with the oval o-ring that goes around the spider or the upper plenum gasket. If you get the oval o-ring aftermarket check to make sure that it does not have any nicks in it. Fel Pro had a huge batch of them in the past that were defective and there still might be some old stock around.

You might want to check the intake gaskets on the lower portion of the intake manifold also as they are prone to leaking. GM also has an updated gaskets for that also.

You will be surprised how much smoother the truck runs with the new injection system.

[wistech]

QUOTE (saltus440 @ Feb 10 2010, 05:18 AM) <{POST_SNAPBACK}>

You are having a problem with the fuel injection spider. The type that came in those trucks from '96-'99 were problematic. They are poppet style injectors that are leaking after the truck has been run and has built fuel pressure. After the truck has been shut off the system is still pressurized and the injectors are leaking into the intake manifold causing it to be hard to start. It starts easily after it has sat all night because all the fuel has had time to evaporate. GM has solved this problem with a revised spider unit that has mini injectors instead of the old poppet style. It comes as a complete spider unit (base, injectors, new regulator). should cost around 300'ish from dealer if I am not mistaken. I can't recall if it comes with the oval o-ring that goes around the spider or the upper plenum gasket. If you get the oval o-ring aftermarket check to make sure that it does not have any nicks in it. Fel Pro had a huge batch of them in the past that were defective and there still might be some old stock around.

You might want to check the intake gaskets on the lower portion of the intake manifold also as they are prone to leaking. GM also has an updated gaskets for that also.

You will be surprised how much smoother the truck runs with the new injection system.

Thats what i was refering to . I never had an issue with any just read about them.

[MX Quad Dad]

Ok. I'll check into that, but one thing seems wrong. I thought 1999 was the first year for the 5.3 engine.

[cannondale27]

I think it was mid 98 when 5.3 came out.Mine is a 2000 and it has regular Multiport FI but I know they had that wierd remote injection system on some 99's since a buddy had it on his.