'89 300-6 running rough
Fleet Mechanic
Joined: Jun 2015
Posts: 1,881
Likes: 296
From: Central Michigan
I had a 96 300 that #6 quit as yours. It was a rusty junker but ran excellent until all of a sudden lost #6 then shook like crazy. Long story short it was a bad connection somewhere between the ecm and #6 injector. I got a wiring diagram, found out which wire went from ecm to #6 injector (actually turns off and on the ground) and spliced in a jumper wire using a spool of 18 gauge wire and 2 trailer wire connectors, Really!! Worked great. Not a good/correct long term fix but good enough for this rusty beast then truck ran great again.
Logistics Pro
Joined: Dec 2003
Posts: 3,782
Likes: 876
From: Foothills of NC
Injector of bad wire in the harness. Dang I was hoping that would fix it.
If you can figure out which color wire is the #6 injector wire at the ECM plug and run a splice in it to the injector plug, that would be a start. You are probably going to have to take the upper intake off and pull the spark plugs, then do a crank over noid light test on #6.
If you can figure out which color wire is the #6 injector wire at the ECM plug and run a splice in it to the injector plug, that would be a start. You are probably going to have to take the upper intake off and pull the spark plugs, then do a crank over noid light test on #6.
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Tuned
Joined: Oct 2001
Posts: 483
Likes: 6
From: Pelzer, SC
ok, I pulled the upper plenum for access to the injector connector. Bought a noid lite kit, but the lite for the Fords the pins don't line up good with the connector.
One of the lights labeled GM does line up good. But when I spin it over there is no lite up.
Do I have to pull the spark plugs for the noid lite test??
And we're off…………………….again.
One of the lights labeled GM does line up good. But when I spin it over there is no lite up.
Do I have to pull the spark plugs for the noid lite test??
And we're off…………………….again.
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Tuned
Joined: Oct 2001
Posts: 483
Likes: 6
From: Pelzer, SC
I noticed also that the fuel pump does not come on for a couple seconds when I turn the switch. So therefore, the injectors would not fire???????????
It would purge before I removed the upper intake??
It would purge before I removed the upper intake??
FTE Legend
Joined: Nov 2015
Posts: 30,961
Likes: 4,129
From: Angier, NC
AFAIK the injectors do not fire or you would loose any psi it built up with the key turned to on.
Dave ----
Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
My understanding of EFI (80-86) when you first turn the key on the fuel pump should run for a few seconds to prime / build psi in the fuel rail / system before you turn the key to start.
AFAIK the injectors do not fire or you would loose any psi it built up with the key turned to on.
Dave ----
AFAIK the injectors do not fire or you would loose any psi it built up with the key turned to on.
Dave ----
Thread Starter
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Tuned
Joined: Oct 2001
Posts: 483
Likes: 6
From: Pelzer, SC
Well gee whiz, the injector checked out good and the other 5 did too.
I still swapped cyl 6 inj with cyl 3 inj.
And it still don't matter. The motor still runs rough and pulling cyl 6 wire still makes no difference in running rough.
I am tired.
I still swapped cyl 6 inj with cyl 3 inj.
And it still don't matter. The motor still runs rough and pulling cyl 6 wire still makes no difference in running rough.
I am tired.
Cargo Master
Joined: Jan 2019
Posts: 3,369
Likes: 16
From: Caraway, AR
No change means you found the culprit. Number six wire. If it doesn't make it worse when you pull it, it's bad. You do like the rest of us? Save your old set for emergencies? Run another wire on there. I mean you could check by swapping wires to see if it moves to another cylinder, but if your ears aren't any better than mine I have trouble hearing. You got a spark tester? Could be a plug or wire come to think of it. Swap five and six wires, if not change swap plugs. I haven't read the entire thread, so don't know what's new, but a new set of $2 plugs never hurt.