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expert on mpfi ea81t needed


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1988 gl10 auto awd. My son went to lunch and it refused to start , stranding him. Compression is 100,95,90,75 . The plugs , cap , and rotor are new, Timing belts are new. Fuel pressure looks good, Spark looks good when a plug is laying out but an inline spark tester looks weak on 3 out of 4 wires. I swapped the coil and pretty much no change. After attempting to start , the plugs were soaked with gas. If I pull the line off the filter there is no pressure in it until I hit the key. Could the injectors be letting an excess of fuel dump in the cylinders? Is it more common to have a spark problem erupt suddenly - neither one seems likely but nevertheless - it does not run.

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do a search for 'timing belt procedure" and double check the timing marks.

 

maybe you should replace the coolant temp sensors ,as when it goes bad, the car is difficult to start when wam.

 

if it is a start then die, and no start again till it sits situation, there is a transistor on the coil bracket that can fail. the coil itself almost never fails.

 

the injectors would not dump excess fuel unless the car thinks its old when actually warm, check cts.

 

the fuel pressure regulator is after the injectors.

 

the fuel pump runs with the key in the start position, or when the car is running, or 2 seconds when the car is frst turned on.

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thanks for the replies ! Yes it is an ea82t - wishful thinking i guess:D. The rotor is still screwed in place and spins , we put the spark tester on each cylinder. The first one had good energy - the shortest wire - all others looked weak to me. I will try that transistor off my spare car - I think a spark problem is much more likely than a fuel one. The suddeness of it breaking makes me think it would be a single point failure ( ie not 3 out of 4 plug wires or all 4 injectors ) thanks! any other ideas?:popcorn:

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the disty is an optical style with 360 notches on a disc. this sends a sgnal to the ecu. The ecu then sends a spark signal to the transistor, and the transistor amplifies the signal to the coil to break the field coil and indice a spark.

 

it is possible that some teeth sheared off the timing belt and caused the disty/cam to be out of time. This would eplain the compression numbers. The lower compression is on the disty side?

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Cant dpo anything untill we have squish fixed really. We have suck, maybe boom.

 

Correct the engine timing first.

 

"Compression is 100,95,90,75 ." And the standard is 145 for this engine. I'm wondering if the excess fuel is washing down the cylinders. Probably is, but still, those numbers should be higher.

 

Doug

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the lower numbers are on the disty side but the old belts look like new - no teeth missing. I am having a lot of trouble finding a new transistor. I tend to think it is weak spark problem because the ignition tester just gloed orange weakly on 3 out of 4 wires - only the short one was bright.

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Can`t help thinking you are barking up the wrong tree re spark,but,I could be wrong.

 

Judging ignition quality by spark colour is an old wive`s tale.

The length of gap it will jump is a better indicator.Spark testers w/an adjustible gap are useful.

 

In addition,the inline testers that connect to the plugs ground through the plug adding another variable to the mix.The type that ground directly to the block and have an adjustible gap are better,IMO.

 

 

Briggs and Straton say:

 

"A bright blue spark is best. A yellow/orange spark signifies weak ignition. Not true. Spark color determines virtually nothing. The hottest spark is ultraviolet which we can't see. Blue spark is cold in comparison to ultra-violet. Orange and yellow come from particles of sodium in the air ionizing in the high energy of the spark gap"

 

The ignition power transistors are normally all or nothing.

 

 

The injectors might be letting an excess of fuel dump in the cylinders.

Might be leaky injector(s),(does the fuel pressure hold after shut down?),

bad MAF,TPS or CTS.

 

I would try starting w/each of the above disconnected alone.

Dry the plugs each time.

 

Those compression #s are pretty bad.I think it should still run though.

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maybe you have a point... the fuel does not hold pressure. I unhook the hose from the fuel filter and there is nothing there until I turn the pump back on. A pressure reg. comes after the injectors - right? It has to be a single point failure that ties to all 4 injectors given the suddeness of it quitting. I will try to find some time to work on it tomorrow. Thanks!

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judging by the compression numbers i would argue the cam timing is off. perhaps the tensioner is loose.

 

you should go through the timing belt procedure and check all that before determining spark or fuel timing, especially since you have compression numbers to prove something is not normal.

 

search this forum or the intenrnet for 'timing belt procedure' and you will find the write-up

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n othat wil not work being a mechanical disty with external knock control. but one frm an spfi will fit. the 86 and 87 spfi has a round plug, 88 and up have a square plig like the mpfi. you can swap the pictail from one to the other to match.

 

the difference between an spfi and an mpfi disty is the spfi has a round shaft, and the mpfi has a d shaped shaft, and the mpfi has a taller cap and rotor. and spfi rotor and cap will fit on an mpfi disty, but not the other way around

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i do have a non turbo spfi disty laying around here. A friend said that the bad gas here may have ruined the injectors allowing gas to dump in cylinders - how likely is that - the hoses amd belts were pretty dried out. Meantime - I am taking offers on the car - would make a great ej22 candidate.

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  • 1 month later...
Turned out to be a bad disty cap. Was recently purchased but went bad within 6 months!

nice hit, good score. so you still driving it?

 

i had a new rotor fail (on an XT6 - same rotor as EA82T maybe) after a couple weeks/month too. the end of it just came apart...guess it too could have been disty failure if it was causing the rotor to tear up - but i seem to recall the rotor looked like the failure point.

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