New Motor, Same old problems

RickyRiot

Registered User
First off, I'd like to thank you all for taking the time to read this and offer any help posssible. I work as a mechanic at a respectable repair shop, and am a bit embarrassed that I am so stumped by this car.

The car in question is a 1990 Ford Thunderbird SuperCoupe, with a 3.8L supercharged engine. It is A manual and has A/C.

This car has been to three different repair shops before I got my hands on it. The last two shops both destroyed the rebuilt engine in attempting to get it to run (fuel washing the cylinders, I would guess).

This time, the engine was removed and installed by a very good tech. He is very thorough and accurate. The engine has been completely rebuilt (ground crank, new bearings, chain, rods, pistons, rings, machined heads, new valves, springs, seals, water pump, belts, cam & crank sensor, plugs, wires, DIS module, MAF sensor, used ECM (EEC-IV), timing set (cam syncronizor set, and double checked with specific tool).

I have good spark and fuel, cranks great. I have injector pulse. I have good gas and fuel pump holds a healthy 38 lbs of pressure for over twenty minutes.

The car will start after a bit of cranking. I can keep it running if I feather the gas pedal. It occasionally will attempt to idle (poorly). When it does idle, it still has positive boost(only about 3 lbs - still too much for idle). I am starting to think that the supercharger itself is bad. Probably bad or coked up valving inside. The tach works fine and no other lights are on at time of cranking. I haven't been able to check any codes in it because it dies before I have had a chance to hook up the scanner. No KOEO codes.


So that is my story. I hope I have provided enough info for you guys to help me out. Getting this car driving again would be great for my job status, and especially my ego.

thanks guys.
 
20-21psi at idle on the gauge
check for leaks ,vac -in the intake system

cheers
 
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Where are you measuring boost??

The car should be running 20 inHg + or - 3 at idle. There is a bypass valve at the back of the SC that should prevent boost at low (idle) rpm to keep the sc from cavitating. It sounds like the problem is related to this, as you shouldn't have high boost at low rpm. I do believe this is a positive displacement blower, so it makes boost at any rpm. The vac line for this diaphram is hard plastic and runs under and around the intake plumbing, so it can get a hole rubbed, or pinched in it. I would watch the diaphram operation from underhood to verify it moves.

Hope this helps.
 
Is the used ECM have the same numbers of the ECM that was replaced?
Are the numbers in the same family ,years of ECMs.

Randy
 
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Ford has a very specific pinpoint diagnostic chart that can be used for no-start conditions on the SC.

It's certainly gonna be available through mitchell or Alldata. Have the mechanics go through the pinpoint test. The blower is unlikely to be the cause of your problem. You can verify this by removing the belt off the blower. A properly running motor will run with the blower disconnected.

I wrote up the pinpoint tests from a 89 here,but it may be different in 90
http://mnharms.com/tutorials/disnostart/
 
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20-21psi at idle on the gauge
check for leaks ,vac -in the intake system

cheers

Hey Guys!

thanks for all the advice. Sorry to get back to the forum so late.(lost internet for two weeks!). The car has been shipped to yet another shop. I don't have a smoke machine - but I think the boss is now convinced we need one. The new mechanic said he found a couple of vacuum leaks but was not very descriptive, and the boss was not able to relay the message very well. I was told it will now run a bit better, but definately not right yet. I will keep you guys informed as soon as someone figures it out.

Oh, before I forget. Mike, that flowchart is very nice. If i run into this car or another one like it, I'm sure it will be of great value to me. Thanks again.

- RickyRiot
 
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