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Mystery Wagon Problem

start hot start

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14 replies to this topic

#1 BestCar/OnlyCar

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Posted 12 August 2013 - 10:03 PM

Let's see if anyone has been through this problem before. I have a late 1988 (manufactured in Sept. uses some 1989 parts Im often told?)  GL wagon. It starts good and runs good. If I don't turn it off (just fill it running at the pump) it will run forever, no problems, but once I turn it off I have to wait 2-5 hours til the engine temp cools down and it will start again. I switched out the ECU and that made no difference. Someone else tested the ignition relay for me and the ECU grounding. Fuel pump has good pressure. It gets spark fine. I tested the temperature sensor, When looking in the fuel injector while trying it I don't see any fuel injection going on. However, one of the three mechanics who looked at the car and gave it back scratching their head (this one at an actual expensive dealership) said he thought it was injecting, but just running lean...I don't know.  My next step is to swap out a new (read different used but hopefully functioning) section of the engine that has the engine wiring harness, Throttle body injector, and a lot of sensors...I might not sound too clear on that because I am only learning about the innards of my car in detail recently.  I could change a tire or an alternator or something, but nothing this involved. In the meantime I have bought another Subaru 1988 GL wagon (yea!) to have something to drive. It was intended originally to maybe donate parts to the other, but now I love both children and neither will be cannibalized! Both will be saved! The new wagon is red, lifted, and I just put 15" wheels on it! If anyone has been through this Let me know your wisdom. 
                                                                                                                                                                   Patty



#2 scoobiedubie

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Posted 12 August 2013 - 10:09 PM

You have to start by narrowing it down between no spark or no gas. Check for no spark by pulling a spark plug wire but holding it close to the plug, and listen for an electical snap. Have somebody else turn the ignition on start. By completely removing the plug, you should smell gas coming out of the spark plug hole, if you are getting gas.

Try replacing the black wire in the fusible link box, near the coolant overflow bottle. They go bad.

#3 MilesFox

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Posted 12 August 2013 - 10:23 PM

Based on your symptoms of not starting until sitting for a while, I would suspect the Ignition Amplifirer module on the coil bracket. This part can overheat and fail until cool, and is also a common instance reported on this site.

 

The crank sensor is the optical disty. The ECU needs to see a signal from this to pulse the injector and the ingnition amplifier.

 

 

If you must replace harness sections (confirmend by continuity testing) anything from 88 and up is the same. 



#4 BestCar/OnlyCar

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Posted 13 August 2013 - 07:34 PM

@Scoobiedubie: as I said, it is getting spark. However, I will find and check the black wire in the fusible link box! Thank you for the suggestion. 

@ MilesFox: I will find out what the Ignition Amplifier module on the coil bracket is and test it. 
as to your statement "The crank sensor is the optical disty" I get what the crank sensor is. I was told that was not it. By one person I was told my car does not have that. And by one person for some reason it did not work with these symptoms I don't recall so I am willing to revisit it. Sadly I only have the Hainz and Chilton and not the manufacturers manual for the car which does not help. How does one go about getting a decent book for the car?  I don't know what "optical disty " means? 
Thank you on the tip on harnesses as well!



#5 BestCar/OnlyCar

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Posted 13 August 2013 - 07:40 PM

@MilesFox: The Ignition Amplifier Module....I have not found this yet, but is this to do with spark as it is on the coil? I am getting good spark. 



#6 MilesFox

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Posted 13 August 2013 - 08:19 PM

This part is located on the coil mounting bracket with blue and yellow wires. It looks like a transistor heat sink.

 

Another part to consider is the engine temp sensor for the ECU. It is located on the thermostat housing and has 2 wires with a green pigtail. This also causes warm fail to starts, particularly with MPFI models.

 

"optical disty' is the distributior. Disty is slang for it. Optical means that is is electronic and not mechanical points or hall sensor. Inside there is a disc with 360 slots and an infrared LED counts the rotations. This part acts as a sensor internally for the ECU, which pulses the ECU, which in tirn pulses the Ignition Amplifier module, which energizes the coil and breaks the field circuit to induce a spark. The top half of the distributor serves to distribute the spar to the plugs,

 

In an analogy, the ignition amplifier module acts the same as points do in an old system in regard to the coil. the schamatics you want to look at would be labeled something like "typical 1988 and later engine management" 

 

The haynes book borrows a lot of diagrams from the factory service manual, but some of the text reads as if it is european english/british translation.

 

The electrical schematics are pretty good in the haynes book provided you know electrical troubleshooting techniques.



#7 BestCar/OnlyCar

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Posted 14 August 2013 - 01:48 AM

@ MilesFox:
Hi Miles, thanks for your reply. Its not the temp sensor. Already tested that. If I get what you are saying with the Ignition amplifier module the answer is yes. it is part of supplying spark. It is good to know about this part, but since I get good spark without fail it can't logically be the answer to this particular problem right?



#8 MilesFox

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Posted 15 August 2013 - 10:31 AM

If you think it may be fuelin issues, try inspecting the fuel pressure regulator. In rference to a fuel schematic, the regulator is AFTER the injector. It is mounted near the throttle body.

 

Have you disconnected any fuel lines, as it is possible that they could have been reversed if so.

 

Also, just for troubleshooting's sake, have you verified the timing belt alignment? 

 

Ypu can test the fuel pump by connecting the test connectors under the dash near the ECU. for 1988 the test connectors may be near the windshiled wiper motor. Ther ewill  be apair of green connectors. When these are plugged in, it will cycle the fuel pump relay for 2 seconds at a time so you can test the circuit or the pressure.



#9 BestCar/OnlyCar

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Posted 15 August 2013 - 03:54 PM

Hi Miles,
I have not removed any fuel lines. The fuel pressure is good as verified by disconnecting one side of the hose as it goes into the engine and putting a pressure guage (sp?) on it.
If there was something wrong with the timing belt alignment wouldn't that make it not able to run perfectly well when I only run it once? (forgove me, I dont know that much about these things yet)
I will try to look at the fuel pressure regulator and learn its function and explore if this could be a cause! 
                                                                                                                                                  Thank You,

                                                                                                                                                                  Patty



#10 MilesFox

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Posted 15 August 2013 - 08:25 PM

The belt could have jumped a tooth if the tensioners are not tightened properly. This should only be suspected if the timing belts were recently serviced, and in a loose bolt that was forgotten to be tightened.

 

Make sure all the intake boots are connectoed properly, no loose clamps. 

 

Try testing your fuel pressure on the return line as well and compare the readings. In theory the pressure would be lower after the regulator if the injector is indeed working.

 

Everything grounds at the ECU, so i am now wondering if a resistor in the ECU circuit board could be failing.

 

There have been instances reported here of resistors in the ecu overheating and failing, and even de-soldering themselves. 

 

anything 88 and up for an ecu wold be plug and play if you come to this conclusion.



#11 BestCar/OnlyCar

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Posted 16 August 2013 - 10:43 PM

@Milies: Thanks for your further thoughts. I switched out the ECU first thing and it did not resolve the problem sadly.Happily It was quite simple as you say. Timing belts were not done recently. Plus, again, wouldn't that affect how it runs? Not just that it wont start once it has a hot engine?
I have not gotten a chance to play around with it lately. I have been taking care of the one I bought to drive while I sort this one, and also took an engine in to be re-manufactured. Man. These cars need more care than kids!



#12 Skysm182

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Posted 16 August 2013 - 11:07 PM

I am very interested in where this thread goes. I had this same problem this spring where i started the car, drove it 3 minutes, stopped for gas, and it wouldnt start back up til i came back hours later to possibly tow it. havent had that problem since.

Edited by Skysm182, 16 August 2013 - 11:08 PM.


#13 MilesFox

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Posted 16 August 2013 - 11:54 PM

I still think you should consider replacing the ign amp module.

#14 Cougar

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Posted 17 August 2013 - 02:35 AM

Try spraying some starter fluid into the intake while the trouble is happening. If the engine runs with that then it appears there is a fuel delivery problem. If it still doesn't run then I think MilesFox is correct about the ignition amplifier being faulty. It has fooled a lot of folks in the past. You can get factory service manuals on Ebay. There is no substitute for them. 



#15 Gloyale

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Posted 17 August 2013 - 03:50 PM

@ MilesFox:
Hi Miles, thanks for your reply. Its not the temp sensor. Already tested that. If I get what you are saying with the Ignition amplifier module the answer is yes. it is part of supplying spark. It is good to know about this part, but since I get good spark without fail it can't logically be the answer to this particular problem right?

 

How did you test the Temp sensor?  and did you test the correct one?

 

The one the ECU uses for enrichment is the 2 wire one with the Green pigtail lead on it.  Try disconnecting it the next time it won't start.







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