Chasing harness/idm/injector related issues

powerstroker66

New member
Joined
Nov 12, 2012
Messages
236
Reaction score
0
Location
pipersville, PA
Hi all,

ive been battling an electrical issue with a 99' f550 for some time now. When i first got it the truck ran very rough, no power, bad miss(es). New cam sensor/clean fuel/filter it was running much better but noticeable miss. Ended up replacing 7 of the 8 injectors due to rusty fuel trashing the plungers. Still threw contribution faults on the cylinders that had new injectors. After buzz test it came back with P1294...so i replaced IDM and now it runs a little better but still has a long crank and a miss. Driving the truck it doesn't seem to be down on power at all and and miss hardly noticeable if at all at 2k rpms. Buzz test again and now i have a P1271 for cylinder #1. UVC harness good and ohmed out good, engine harness looks good, fresh OEM cam sensor, and known good IDM. Im starting to think the actual engine harness might have a problem? What do you guys think? Thanks!
 

Arisley

Moderator
Joined
May 18, 2011
Messages
9,378
Reaction score
25
Location
Arlington, Texas
Check the little fittings where the fuel lines go into the heads. They are actually one way check valves. Little bitty ones. They are also twenty years old. And you replaced injectors because of bad fuel. I would also replace that eigth injector, that way you will have eight fresh injectors.

BTW, you can safely bore out those check valves with a drill. Go slowly and clean them out really well before putting them back in.
 

mandkole

Active member
Joined
Jan 14, 2012
Messages
2,303
Reaction score
2
Location
Northwest
^^^ good suggestion on the fuel adapters-- but if it's not down on power, fuel flow is likely ok.

Brand new injectors? Not remans? Good buzz test? All OEM sensors, harnesses? Not replacing #8 is odd.. does idle quality change from cold to hot? May want to consider swapping one inj with another to see if the fault follows it.
 

powerstroker66

New member
Joined
Nov 12, 2012
Messages
236
Reaction score
0
Location
pipersville, PA
No #8 injector has been done but still throwing a contribution code. And yess runs smoother when warm not much but noticeable. It has a slight fuel knock miss in one or 2 injectors you can hear it especially cold. All buzz test good other then P1271 open #1 code. Im going to pin the harness tomorrow and check ohms on injector solenoids. I have a hunch a wire is shorting to ground and screwing up timing on one injector which is causing it to "knock/tap" throw and open code.
 

powerstroker66

New member
Joined
Nov 12, 2012
Messages
236
Reaction score
0
Location
pipersville, PA
Alight so i was getting a P1294 high side open bank code. Pinned everything out with o ohms resistance, all injectors cam in at around 3 ohms, etc. so i swapped in another idm. This time it threw a P1271 Cylinder #1 high to low open but no P1294 code and vise versa when swapping between idms. Is it possible i have 2 bad idms? other then swapping these idms into a known good running truck, what other options do i have? running out of ideas here as to what it can be...
 

mandkole

Active member
Joined
Jan 14, 2012
Messages
2,303
Reaction score
2
Location
Northwest
^^yep, check harness. If no issues look at swapping a couple injs to see if the issue follows. Could be a bad injector. Swamps could test the idm.
 

powerstroker66

New member
Joined
Nov 12, 2012
Messages
236
Reaction score
0
Location
pipersville, PA
pinned out both harnesses, no burnt pins, no rubbed wires in either harness, pinned all the way out to the idm for all 8 injectors for continuity, ohmed out the injector coils, checked to make sure non were loose, etc. Have checked everything from the injectors to the idm which is why i think possibly a faulty idm. The truck this other IDM came out of had other issues so weather or not the idm was part of it im not sure. Since the same codes are not present between both IDMs makes me wonder..
 

powerstroker66

New member
Joined
Nov 12, 2012
Messages
236
Reaction score
0
Location
pipersville, PA
UPDATE: i pulled both valve covers and ran the truck. All injectors are firing except cylinder #8 is a no go. However, it is a new injector AND it buzz tests fine. Is it possible there is a stuck plunger? I tried both IDMs and there is no difference. Both idms #8 is not firing and i get contribution codes for both #8 and #3. What do you guys think?
 

m j

Active member
Joined
Jan 13, 2013
Messages
1,225
Reaction score
0
Location
BC Canada Eh!
move the injector to a different hole and see if the issue follows the injector or stays at that hole
 

mandkole

Active member
Joined
Jan 14, 2012
Messages
2,303
Reaction score
2
Location
Northwest
Pull the solenoid off and check to see if the armature plate is loose on the poppet. Loose armature will rattle but the inj doesn't move. You might need the special torx bit (the Nintendo tool) for the screws.
 

powerstroker66

New member
Joined
Nov 12, 2012
Messages
236
Reaction score
0
Location
pipersville, PA
yes they have the center pins int the torx heads. Ive decide im going to test the idm on a known running truck and if they are good then ill pull the injector and send for warranty since i just bought it. Its a alliant reman from injectors direct so there usually pretty good but ive seen weirder stuff happen..
 

powerstroker66

New member
Joined
Nov 12, 2012
Messages
236
Reaction score
0
Location
pipersville, PA
tested both IDMs on a known good truck and they were fine. double checked and pinned the wire from the #8 injector to the idm pin and have a good connection so i think the culprit is a bad reman injector. I pulled the armature off to make sure plate wasn't loose and everything was fine. Either way i pulled the injector and sending in for warranty now will see what they say. Injector tip was clean like it never fired at all..
 

Latest posts

Members online

Top