2.8L MPFI starting problems MAYDAY!! - Team Camaro Tech
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post #1 of 7 (permalink) Old Jun 3rd, 06, 02:22 PM Thread Starter
 
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Exclamation 2.8L MPFI starting problems MAYDAY!!

It just shut off 2 blocks from the house and now won't start most of the time. When it does, it idles fine, but whenI hit the gas, it bogs really bad. Replaced the fuel filter with no difference. Didn't think to turn the key on with the filter loose to see if it shot gas across the yard. Help!
By the way......1985 2.8 MPFI 120K mi.
Will try the loose filter thing later. If that's good, maybe the timing chain jumped a tooth??????
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post #2 of 7 (permalink) Old Jun 3rd, 06, 02:32 PM
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Re: 2.8L MPFI starting problems MAYDAY!!

It sure does sound like the fuel pump is going away.

You should put a fuel pressure gauge on it, fuel spraying out of the filter isn't good enough.

There is a test port just in front of the distributor. It should have 38-42 psi.

The car will idle with pressure as low as 20, but will act just like you describe.

That's why you can't tell anything without the proper test equipment.

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post #3 of 7 (permalink) Old Jun 4th, 06, 09:59 AM Thread Starter
 
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Re: 2.8L MPFI starting problems MAYDAY!!

Found a pressure guage. Sits at 40lbs with key on. Bleeds down to 30 after about 5 minutes, so that looks OK. It's firing, but the spark is yellow. It's been that way for years, so I don't think that's the main problem. ECM?? I think I can smell gas in the exhaust, so I think the injectors are working. I'm a baffled shadetree.
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post #4 of 7 (permalink) Old Jun 6th, 06, 10:34 AM
 
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Re: 2.8L MPFI starting problems MAYDAY!!

I had almost an identical problem. It turned out to be the catalytic converter. the insides had broken down and had clogged it up so when it starts trying to move a serious volume of exhaust the backpressure shuts it right down. Not saying this is it but it sounds awful close to how I experienced it.

Hope that helps.


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post #5 of 7 (permalink) Old Jun 6th, 06, 06:11 PM Thread Starter
 
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Re: 2.8L MPFI starting problems MAYDAY!!

Kirgan, not sure that would be it. It acts like it's not getting fuel at all. Won't fire off. I've tried cranking it for 15-20 minutes before it would crank, then took 2 or 3 minutes to coax it one block down the street. Had a local "engine guy" suggest the ECM and/or coil, then timing chain, in that order, but would I even get a spark with a bad ECM??? I know a new coil would give me a blue spark again. I'll kill myself if it's a timing chain! I REALLY hate replacing those!!
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post #6 of 7 (permalink) Old Jun 7th, 06, 03:27 AM
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Re: 2.8L MPFI starting problems MAYDAY!!

Usally a timing chain will jump when the engine is shut off, not necessarily while running.

Have an assistant at the ignition key and you observe the the spark plug and screwdriver to ground trick while it cranks. as you've said, it should be a blue spark for 1/4 inch gap, if battery is good charged.

Remove spark plug(s) to see if they are wet with fuel. If wet, then injectors are working. Speaking of injectors, see/measure if there is 12 volts to one side of the injector connector on both sides of the engine. Each side is powered by a relay and fuse. ECM lowers the voltage on the other wire in the connector to turn on the injector. Food for thought there. Power comes from a fused wire from starter solenoid.

If spark plug is out, do a compression check to the one cylinder. If compression is lower than 100 PSI, then maybe the timing chain did jump, but I doubt it.

Check timing chain slack. Turn engine over by hand to timing marks align, then rotate backwards. You will feel the slack. Anything over 10* means the chain is stretched.

You're sure the engine didn't overheat?
You're sure the charging system is working?
EGR valve isn't stuck open?

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post #7 of 7 (permalink) Old Jun 11th, 06, 06:32 PM Thread Starter
 
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Re: 2.8L MPFI starting problems MAYDAY!!

O.K., found the problem. %^&*(^#@ It was the coil. Don't understand how it just suddenly wasn't happy with yellow spark, but.......
Spent the rest of the weekend repairing the exhaust. Gee, that was fun too!! Thanks for all your advice, guys. All the notes have been filed for future reference!! Have a lovely!!
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