86 s-10 no power to injector

[general poot]

1986 s10 2.5 engine with TBI. This truck will not start cold but will when warm.One morning even though it was cranking over normal we decided to jump it with another vehicle and it started right up.We checked the injector with a noid light and it showed no power to the injector untill we put the jumper cables back on.We checked the codes and got a 34, which indicated a bad MAP sensor. I replaced that without possitive results. The TPS had been replaced 6 months ago so I don't think that would be the problem.I have checked all connections,the fuel pump is holding good pressure. Could it be a bad PROM in the ECM? Thank you in advance.

[Mikado14]

Originally Posted by general poot

1986 s10 2.5 engine with TBI. This truck will not start cold but will when warm.One morning even though it was cranking over normal we decided to jump it with another vehicle and it started right up.We checked the injector with a noid light and it showed no power to the injector untill we put the jumper cables back on.We checked the codes and got a 34, which indicated a bad MAP sensor. I replaced that without possitive results. The TPS had been replaced 6 months ago so I don't think that would be the problem.I have checked all connections,the fuel pump is holding good pressure. Could it be a bad PROM in the ECM? Thank you in advance.

You found your problem. Your battery voltage is dropping when you crank and is not sufficient for the ECM. When you jumped it, that was your answer.

Load test the battery and you will probably find it is below par.

[general poot]

Originally Posted by Mikado14

You found your problem. Your battery voltage is dropping when you crank and is not sufficient for the ECM. When you jumped it, that was your answer.

Load test the battery and you will probably find it is below par.

I thank you for the reply. I wish it was that simple. We tried a brand new battery from another car with no luck.

[ltedt]

had this problem once with my 87 s 10 (poor thing died after JUST 255K miles) Anyway i had a broken ground wire that attached to the rear of the driver side cylinder head.
Fixed the ground wire and never happened again.
Matt

[general poot]

Originally Posted by ltedt

had this problem once with my 87 s 10 (poor thing died after JUST 255K miles) Anyway i had a broken ground wire that attached to the rear of the driver side cylinder head.
Fixed the ground wire and never happened again.
Matt

Thanks, We checked all grounds and found nothing wrong. The truck is now acting different. It won,t start now, even when we try to jump it, I have put a used ecm on it ( yes, I changed the mem-cal (prom). I have put on a new map sensor, est, trottle sensor, and fuel pump relay. With the key on, the noid light flickers erraticaly. Can someone please help?

[Mikado14]

You said that when you jumped it, it started.

Perhaps checking your battery cables and looking for expanded insulation or corrosion within the cable at the ends. OR take a DVOM and measure the resistance of the Pos and Neg cables. Eliminate them from the equation.

[BlazerLT]

Also, clean the battery cable connections.

Also, did you charge the new battery up before installing it?

[general poot]

Originally Posted by BlazerLT

Also, clean the battery cable connections.

Also, did you charge the new battery up before installing it?

We found it!!!!! The beaker plate in the distribitor was very worn. The Hall effect switch is mounted to the breaker plate. This switch sends RPM information to the ECM. By the switch not holding the correct posistion it was sending eratic information. We installed a new breaker plate,pick up coil, and Hall effect switch and the truck has never ran better!!! It puzzles me why the extra amps from a jump would make a difference. Oh well it runs great!! Thanks to all for their replies and have a Merry Christmas!!!!