Starting problems..ECU Rebuilt but still no start

I appreciate any help you guys can offer. One morning, I went to crank my t-100(97 with 260,000 miles) and it turned over fine but it didn't start. I continued to turn it over, off and on for probably 2-3 minutes. It was acting like it wasn't getting fire. Finally, it cranked like it wasn't having any problems. I drove it around a while...stopped and shut it off and came back later and it started first try. Over the next few days, it did the same thing as I stated first, probably 50% of the time.

I took it to pep boys and they did an engine diagnostic test and it came back saying the ecu/computer was bad. I then drove home and it never started again...would turn over but no matter how long I tried, it wouldn't start. I sent the ecu off and had it rebuilt...I got it back today and installed it and it's doing the exact same thing as before...turns over fine but doesn't start.

I called the technician back and he said it tested fine before he sent it back to me.

Does anyone have any idea of what could be wrong?

Just to clarify...the starter is fine...the alternator is fine and the battery is fine.

Thanks in advance...

Heath

I would try some troubleshooting when it is malfunctioning. Is the engine getting fuel? If so, one possible cause is a faulty MAF. It wouldn't hurt to make sure your fuel filter is ok. (that would be a cheap and quick thing to check first.) Is it getting spark? I certainly don't know all of the possible causes, but someone here might have some ideas if given some more symptoms.

With 260k miles on the engine, I would suspect something worn mechanically or corroded (causing electrical problems). I wouldn't expect the ECU itself to be intermittent. Semiconductors usually fail completely, not intermittently.

I just had a similiar prob on my 3.0L. It was blowing the main EFI 15 amp fuse. Engine would turn over but would not start. I traced and checked all the wiring and relays. It ended up being the fuel pump. Turn the key to the start position but do not start the motor. Go behind the truck and listen to see if your fuel pump is running. If it is not then you know which direction to go from there. This may not be your prob, but I hope it helps. good luck.

the most common fault is the main efi relay, when you turn the ign switch on does the engine check light come on? if it doesnt go to the diagnostic plug and check for 12 volts on the B+ terminal if not replace main efi relay, if there is do fuel pump check

the most common fault is the main efi relay, when you turn the ign switch on does the engine check light come on? if it doesnt go to the diagnostic plug and check for 12 volts on the B+ terminal if not replace main efi relay, if there is do fuel p pump check

I have a friend w/a '95 T-100 and it has an intermittent start problem like it's not getting fuel. He'll let the truck sit for a while ,then he'll try starting and it will fire and run fine. I think this relay might be the cause but, where is it?? Thanks for the help my friends!!

Main EFI relay?
Quote:
Originally Posted by Klaas van Maane
the most common fault is the main efi relay, when you turn the ign switch on does the engine check light come on? if it doesnt go to the diagnostic plug and check for 12 volts on the B+ terminal if not replace main efi relay, if there is do fuel p pump check


I have a friend w/a '95 T-100 and it has an intermittent start problem like it's not getting fuel. He'll let the truck sit for a while ,then he'll try starting and it will fire and run fine. I think this relay might be the cause but, where is it?? Thanks for the help my friends!!




It is in the fuse box located in the engine compartment.