740 GLE '88 no start

mistaboins · Post by **mistaboins** » 10 Apr 2009, 23:02

hello all,
i have an '88 740 non-turbo which i recently purchased and drove for about a week before my real adventure began. one night it refused to start at the store, i waited a few minutes checked under the hood and it started! a week later on the way home from work, no start... at all. cranked but no start. the next day got it started by unhooking the air mass filter, and limping home. started researching websites for info and repaired cracked wires in the hall sensor, started but once again got stranded. got a new main fuel pump and it worked for one trip, but once again got stranded the next day. discovered that the ground from the battery to the engine block was frayed and was shorting out. was able to start the car, but it would stall by the time i shifted into 2nd gear. went and purchased a new battery cable and installed and it has not started again. right back where i started! cranks but no start.
is it a bad ECU? i don't want to purchase one if i really don't need one. when the car runs it runs great. i'm afraid i'm stuck and need some advice.

Post by **billofdurham** » 11 Apr 2009, 12:03

Welcome to Matthew's Volvo Site.

Is the air mass meter reconnected? If so does the car start with it disconnected? Do you have fuel and spark at the engine?

There are several possible causes for poor/no starting:
Bad or dirty connections on the ignition and plug circuits.
Air intake leakage.
Fuel pressure incorrect.
Temperature sensor defect.
Fuel pump relay/circuit.
Vacuum leak.

Bill.

mistaboins · Post by **mistaboins** » 11 Apr 2009, 13:04

yes air mass is reconnected, and no it still won't start, and yes it is getting fuel and spark, but still no start.

mistaboins · Post by **mistaboins** » 11 Apr 2009, 15:43

also new fuel pump and relay, temp sensor, vacuum all look good, how to test fuel pressure?

Post by **billofdurham** » 11 Apr 2009, 15:59

Which temp sensor did you replace? Your car has two, one for the gauge and one for the ECU.

740 fuel pressure.pdf: Fuel pressure check; (179.88 KiB) Downloaded 152 times

Bill.

mistaboins · Post by **mistaboins** » 11 Apr 2009, 16:07

bill;
thank you for the file and advice, i changed out the sensor on the passenger side towards the front, not sure if it's the correct one or not.

Kmaniac in California USA · Post by **Kmaniac in California USA** » 11 Apr 2009, 17:32

Your post said you changed the main fuel pump, which I assume is the one under the car below the driver's seat. Your car has TWO fuel pumps. Did you replace or even inspect the in-tank fuel pump?? Check fuse #11, the one for the in-tank fuel pump. If blown, it is time to replace it and the in-tank filter sock. Now, if you replaced the main fuel pump (under car) without even inspecting the in-tank pump, you run the risk of sucking dirt through a holey in-tank filter sock and ruining the new main pump within days of replacement, resulting in an intermittant or permanent "no start" condition. Both pumps should be replaced at the same time to prevent this from happening. Search this forum for my posts on fuel pumps. Most of these posts are over four years old.

Kmaniac in California USA · Post by **Kmaniac in California USA** » 11 Apr 2009, 17:36

mistaboins wrote:bill;
thank you for the file and advice, i changed out the sensor on the passenger side towards the front, not sure if it's the correct one or not.

The temperature sensor towards the front of the engine is the gauge sensor. The one towards the rear of the engine is the ECU sensor. The latter sensor is designed to temporarily advance the ignition timing during warm up when coolant temperature is below 40 degrees F at cold start up. I doubt this sensor would be your problem.

mistaboins · Post by **mistaboins** » 14 Apr 2009, 13:25

thanks to all who responded, it turned out to be the radio suppression relay,(which must have fried when shorted out) but we're back running!

Post by **billofdurham** » 14 Apr 2009, 15:54

Thank you for the update. That is one that is usually overlooked.

Bill.