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john aka eaut
john aka eaut, The Car Guy
Category: Pontiac
Satisfied Customers: 15883
Experience:  15 years as a auto tech
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89 Pontiac Bonniville, cranks no start after warm replaced

Customer Question

89 Pontiac Bonniville, cranks no start after warm replaced crank and cam sensors and fuel pressure good ,now what?
Submitted: 1 year ago.
Category: Pontiac
Expert:  john aka eaut replied 1 year ago.

when it does not start you need to check the basics.. will have to pinpoint what the engine is missing.

Spark

Fuel

Compression

All three of these are tested when the engine is being cranked over. There are two way of checking for fuel. Fuel pressure and fuel trigger. Both are very important and must be present for the car to start. Fuel pressure is self explanatory. You just hook up the gage and see what the reading is. Fuel trigger is check with a noid light. The injector gets unplugged and the noid light gets plugged in to the injector clip. With the engine cranking over, this light must blink. This is the signal to the injectors from the computer. You can have all the fuel pressure in the world, but it wont matter if the injector is not pulsing gas into the cylinder like it should! Compression tester, spark tester, fuel pressure gage and noid light are all accessible

Customer: replied 1 year ago.
I have work as a mechanic for 30 yrs last 15 ford ,so all the basics are done, im thinking its something with ECM , any secret pontiac shit you know about to be sure im in rt dirrection
Expert:  john aka eaut replied 1 year ago.

early on these did have a batch of bad computers...I changed so many of them I use to have the part number memorized...they had week sodder joints..but ignition modules were very common also

Customer: replied 1 year ago.
No disrespect , what is a fast check you would use to say ok needs a computor
Expert:  john aka eaut replied 1 year ago.

they use to intermittently stall , and gm had the techs o a simple tap test...tap on the pcm if the car stalled replace it...but you have a no start... very limited data can be pulled out of these is you have a old mt 2500 or a old tech scan tool..

here is the old tsb..

Some control module's may have problems due to cracked solder joints on the circuit board. These internal control module problems can cause the following symptoms:

  • Failure to start or vehicle is stalling.
  • The "CHECK ENGINE" "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR" light will flash or light up, but no trouble codes will be present.
  • Vehicle instrument panel displays may be inoperative.
  • The control module may or may not communicate with the scanner.
  • Other intermittent driveability problems.

Incorrect PROM or MEMCAL removal and replacement can create solder joint problems or aggravate an existing condition. See PROM or MEMCAL INSTALLATION for proper procedures.

If a solder joint problem results in a "hard" failure, normal test procedures will usually pinpoint a faulty control module. Many symptoms caused by poor solder joints in the control module result in intermittent problems, but they may be hard to duplicate during troubleshooting. Control module's with solder joint problems are sensitive to heat and vibration. You can check for these internal control module problems in either, or both, of the following ways:

  • Remove the control module from its mounting bracket and extend it on the harness so that you can expose it to the vehicle heater ducts. Alternatively, use flexible ducting to route air from the heater to the control module location. Then run the engine and operate the heater at the "MAX HEAT" position. This exposes the control module to approximately 140°F.
  • With the engine running, tap on the control module several times with your hand or finger tips to simulate vehicle vibration.

If the engine stumbles or stalls, the "CHECK ENGINE" "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR" light flashes, or any of the previous symptoms occur, the control module may have bad solder joints on the circuit board.

Customer: replied 1 year ago.
Thats what im talking about the secret, shit.hey man thanks ima god do this now, if i need more info i request you
Expert:  john aka eaut replied 1 year ago.

lol hope you can rate me excellent

Customer: replied 1 year ago.
I rate the tech as expert, and my spelling sucks without glass,s. My last statment was ima go do this. Now....not god. Do this,,.thanks again , the comp bad
Expert:  john aka eaut replied 1 year ago.

hope you can rate my service 5 start or excellent

Expert:  john aka eaut replied 1 year ago.

hope you can rate my service 5 start or excellent...that's the only way I get credit for my advice, time and knowledge