got my new engine running but it wont run on my computer! Only will run off scanner

[asabadin]

ok here is the deaL. please keep in mind i am not too knowledgable with this sort of thing. my burb is a 1995 and i put a rebuilt drop in that was out of a 98(engine year is 97) after thinking it was my injection pump, we were on the line with a tech and we were able to fire up the engine no problem but it was running of the scanner and not the computer. we sent some kind of command to the selinoid and the engine fired right up after a couple of cranks!!!! appertantly we were getting zero codes or readouts from the truck"s computer.
when we disconnect it and try to run it off the truck computer, no dice!!! we checked all the connections all of them are ok no shorts busted fuses or loose wires at all. i was now told that we need a whole new computer? is that correct?
is there another explination to this problem or a cheaper way to fix this thing right the first time? if not where do i get the most reliable computer for the best price? has anyone else had this problem??????? help is needed!!! i know you boys have the answer

[charliepeterson]

The donor engine is looking for an OBD II program. The truck has an OBD I program. These programs are close but don't work together. Try looking in your local bone yard for a compatible computer.

[asabadin]

my engine is a f code. do i need a "f" vin code computer from a 98 for it to run?

[patrick m.]

if you were able to put the engine in, and hook up all of the wires, and your computer is still plugged into the same connectors, the engine wont care what year your truck is.

or if it is OBD2 or 1.

if it only runs with the scanner hooked up, there is probably a ground wire off/broken somewhere.

[gmctd]

The '97 engine harness is a little different in wiring point terminations - you may be running in Limp Mode from the scanner.

Limp Mode has Extended Start function with PCM - takes greater than 15secs cranking before starting.

If you tied the '95 harness into the '97 engine, the scanner may be running in Limp Mode if you overlooked the Crank Position Sensor connector - runs across in front of the Inj Pump, CPS harness comes from down the drivers-side of the timing cover.

Or, the Optical Sensor connector, etc.

[Kennedy]

Just be sure to use the 95 wiring, and you should be fine. I am assuming you are still using the OE accessories (AC, alternator etc) so from there, it should all just transfer over to the new engine.

Check all of your grounds back at the coolant block off plate on the RH rear of the engine.

Do yourself a favor now, and tighten the studs securely using Loctite , and use NOTHING on the nuts. It really sux when the studs spin with the nuts and you can't get a wrench on the stud hex...

[asabadin]

thank kennedy and everyone else going to see if i can chase this problem down today!!

[jdmetcalf57]

Just take your time and logically figure out what it could be. It is probably something you didn't quite get back together right.

I have a lot of experience in figuring out problems on a lot of diffeerent types of machines and there is one common problem with the way most people do it. They start changing things before they find the root of the problem. In doing this they usually do not fix the problem correctly and they often create other problems.

If it is one thing that I have learned it is that if it doesn't make sense it probably is not correct.

[k3500]

I think I had the same problem. I had to replace heads on mine. I put it all together and tried to crank it and nothing happened. I plugged in my scanner and truck fired up. I let it run a while then unplugged scanner, the truck died. With a little research the truck lost a ground somewhere. I never found out where, I ran a new ground wire to computer case. Have you figured out what went wrong with yours?

[Kennedy]

I believe it was a faulty "rebuilt" injection pump if memory serves.

[asabadin]

Grounded out wiring and bad rebuilt ip pump. runs fine now . I've put 1500 miles on it no sweat. Thanks to all who helped especially kennedy diesel.

P.s. Your chip works great!!!!!