92 D21 Computer Fuel probs?

mentawai69 · Nov 5th, 2009, 06:32 PM

This truck has 178,000 and I got it A YEAR ago.
Its been a good strong truck, about a month ago
I would hear the Fuel pump come on outta the blue.
The truck would be parked and you hear this hum coming from under truck near fuel tank. I thought the pump was going out> and let it be..the truck ran fine.. Untill one day it started surging at highway speeds, I thought that I better go get a fuel pump B4 it goes. Went to the parts store and the guy talked me into a tune up and fuel filter.. I replaced the parts, no dramas except the rotor was difficult to get off, pried it a bit and got it.. The truck ran fine a bit rough, but at least it ran.. I ran it to work after 10 miles it left me on da side of the road.Truck Would Idle but once you gave it gas would sputter and choke out.. got it towed, the mech said he thought it was getting too much gas and that he thought it was the computer> he said he tested the pump and it was fine.. well dunno if the computer can just go like that? and nothing else was effected, lights and all works fine..
i ordered a junked ECM and will try replace it.. any advice..

zanegrey · Nov 5th, 2009, 07:18 PM

the ecm can make the fuel pump stay on all the time..

but b4 replaceing it read the codes...

mentawai69 · Nov 5th, 2009, 10:30 PM

I have read the codes on 2 different sittings.
1st time said 21..
second time said 55.
The 21 code kinda blew me away. I stated thinking
Ignition probs..Crank angle sens etc.. dunno hope the ECM
does the job..
So whats the proceedure
Undo the old one and plug in the new one. start it up?

zanegrey · Nov 6th, 2009, 07:55 AM

what settings ??

if that ecm said 55 n e where then it is fine..

check the fuel pump relay on the inner fender well..

mentawai69 · Nov 6th, 2009, 01:59 PM

No I just had two different readings from the codes..
one reading was 21.
then a week later the reading was 55..
check the relay for what. I have unplugged the relay and
the truck eventually dies..
even with the 55 code the truck still would idle fine,
but seems like the truck is only firing on 2 cyliders..

mentawai69 · Nov 6th, 2009, 02:12 PM

So if you get a 55 code. does that mean the computer is good?
I am getting spark on all cyl. but the injectors are mucking up.
I thought not delivering fuel. But according to mech that looked at it
he said,"it was getting way too much fuel and thats why not firing?
and that it could be the comp...
How to check da relay.. i pulled it while truck running and the truck eventually died..

zanegrey · Nov 6th, 2009, 03:05 PM

generally speaking if the ecm is giving 55 then it is good..

just pulling the relay may not be enough..

just about everytime i run into one that the injectors spray all the time it has been a bad ecm..but that is not to say that is ur trouble..

do you have one to swap out?

mentawai69 · Nov 6th, 2009, 05:05 PM

I just checked the codes again, got 55 in mode 3..
Truck still runs like hell.
In mode 4 the red blinks and stays on, and mode 5
the red blinks.
The relay .. what more can you do to the relay. change it out?
how about fuel regulator.
I thought that when changing the fuel filter that some dirt
got past the filter and could have effected the injectors.
But the mech I had it at said the injectors are spraying too much.
he got that from pulling the plugs and an ohm reading at the injector.
the ohm reading was 20 ohms.

zanegrey · Nov 7th, 2009, 10:22 AM

just swap the relay with another green one..

i have those ecms if you cannot find one..

there should be a fuel pressure reg close to the fuel rail..

mentawai69 · Nov 8th, 2009, 01:53 AM

Could the crank angle sensor have gotten damaged when I had to pry the rotor off.
I wonder if this could make these symptoms?

zanegrey · Nov 8th, 2009, 04:38 PM

if you are getting spark then the cas is working correctly..

and didn't the prob come up b4 u did the tune up???

mentawai69 · Nov 9th, 2009, 01:54 AM

B4 the tune up was just the fuel pump coming on and a bit
sputtery at high speeds.
after the tune up the cylinders started not firing.
Im guessing that only 2 clynders fire right now.

zanegrey · Nov 9th, 2009, 09:43 AM

read the codes and confirm the spark ..

mentawai69 · Nov 10th, 2009, 10:11 PM

Zane, I cleaned up some grounds and pulled the fuel relay banged it around and sprayed elec cleaner on the CAS the truck took a while to start, But when it did It was running on all cylinders and I am getting the 11 code in Mode 111. what now?

zanegrey · Nov 10th, 2009, 10:25 PM

if it is running well now just reset the codes, recheck later and send me a check...

if it is not you broke the dizzy ..

i think i have those dizzies for sale..