1988 v6. 3 cylinders not working. Inj2 fuse blown. Electrical problem? (Page 1/4)
danahart SEP 08, 10:46 AM
1988 Formula manual. V6 2.8 upgraded to 3.1l. Not experienced mechanic but am learning slowly so please explain like I'm 5.

Started losing power a few months back and I realized the 3 front cylinders were not powered and the Inj2 fuse was blown. After swapping the fuse it worked find for a while then blew again. I did a lot of forum research at that time but never found the cause (I'm starting this new thread because the other one was so old - thanks to all who helped back then). Mainly because I swapped out the fuse again and the problem didn't reoccur. I drove it 2-3 times a week on short runs for a couple of months. Then the fuse blew again and now I can't get it out of the driveway without blowing a new fuse.

The fuel injectors were replaced when the previous owner switched to a 3.1 but I haven't opened it up to visually inspect them...I was hoping to avoid that. Based on forum post help when I originally was looking at this issue, I was told the EGR Solenoid shared the same fuse. So today I unplugged the wire harness from the Solenoid, assuming that would eliminate the possibility of that causing the fuse issue. Still has the problem.

My question is a) was unplugging the wire harness from the side of the EGR Solenoid enough to eliminate it as a suspect? I didn't remove the entire thing but I didn't see any other wires going into it. b) what should be my next step? Checking the fuel injectors? I'm not sure what I'd be visually looking for on those or I'm not sure how I'd isolate the broken one unless I just replace them all.
Raydar SEP 08, 01:28 PM
Unplugging the EGR solenoid should take it out of the equation. Period. Nothing else that I know of is powered off of that circuit/fuse.
Maybe (If you can reach) try unplugging the front injectors one at a time. Or if you can get an ohm meter to them, measure the individual injectors. It's possible that one of them has shorted. They should measure around 12-14 ohms. But anything "close" should be okay. You can also unplug the flat connector that feeds ALL the injectors. It'll be located kind of near the MAP sensor and the thermostat housing. If the fuse doesn't blow after you disconnect that connector, it kind of eliminates everything between the fuse block and that connector. Points to a shorted injector or injector harness.
I believe the pink wires (there should be two of them) supply 12V to the injectors all the time.
The ECM fires the injectors by switching ground.

[This message has been edited by Raydar (edited 09-08-2024).]

Patrick SEP 08, 03:05 PM

quote
Originally posted by danahart:

I'm starting this new thread because the other one was so old...



Three months ago is "so old"? You must be very young.


quote
Originally posted by danahart:

So today I unplugged the wire harness from the Solenoid, assuming that would eliminate the possibility of that causing the fuse issue. Still has the problem.



Same answer as so long ago.


quote
Originally posted by Patrick Here:

For a short time, it (unplugging the EGR solenoid) should be okay. Make sure to listen though for any indications of engine ping due to the EGR system not being functional. Also keep in mind that if there's a short in the EGR solenoid harness (rather than the solenoid itself), that the INJ fuse could still blow again.


[This message has been edited by Patrick (edited 09-08-2024).]

Raydar SEP 08, 03:19 PM
So... if you unplug everything fed by that fuse (like the EGR valve, and then the injector harness), and the fuse still blows, then the trouble will almost have to be in the harness, somewhere.
This is based upon the premise that the engine doesn't have to be running for the fuse to blow. (Obviously it won't run with all the injectors disconnected at the flat connector.)
danahart SEP 08, 07:02 PM
Maybe not so young but unfamiliar with this forum and how it treats past posts. The old thread also included a code error that has never reoccurred so I wanted to start with the fresh data that didn't include that old issue. However, I guess that could be related .... but it has never reoccurred. I don't have any dash warnings. I appreciate you help with the old and this new post.

How would I go about testing to see if the harness itself is the issue? Should I cut it off and rewire it back again if all stays the same? Is there an easier way to test it?


quote
Originally posted by Patrick:
danahart SEP 08, 08:06 PM
Thanks and that makes sense. Can I unplug the injector harness without taking off the manifold? Is the connector accessible or does the manifold have to come off?


quote
Originally posted by Raydar:

So... if you unplug everything fed by that fuse (like the EGR valve, and then the injector harness), and the fuse still blows, then the trouble will almost have to be in the harness, somewhere.
This is based upon the premise that the engine doesn't have to be running for the fuse to blow. (Obviously it won't run with all the injectors disconnected at the flat connector.)
Patrick SEP 08, 08:15 PM

quote
Originally posted by Raydar:

This is based upon the premise that the engine doesn't have to be running for the fuse to blow.



It would help to know the answer to this. Does the fuse blow with the ignition key turned to Run without the engine running?
danahart SEP 08, 08:47 PM
It doesn't seem to happen if the engine isn't running. I just tried turning the key but not cranking a bunch of times leaving it for a while as well and couldn't get it to blow. The times I was driving when it blew, I was always hard accelerating up a hill. It has blown in my driveway so I don't think it ONLY happens on high rpm or maybe that is just when I notice it because the sound/power loss is more noticeable. I'll try to do more testing to see if I can nail down a pattern.


quote
Originally posted by Patrick:

It would help to know the answer to this. Does the fuse blow with the ignition key turned to Run without the engine running?
cartercarbaficionado SEP 09, 05:23 AM

quote
Originally posted by danahart:

It doesn't seem to happen if the engine isn't running. I just tried turning the key but not cranking a bunch of times leaving it for a while as well and couldn't get it to blow. The times I was driving when it blew, I was always hard accelerating up a hill. It has blown in my driveway so I don't think it ONLY happens on high rpm or maybe that is just when I notice it because the sound/power loss is more noticeable. I'll try to do more testing to see if I can nail down a pattern.



sounds like the injector is having an intermittent fault. you can check it's power wire to ground to see which injector is shorted. I would actually unplug your cold start Injector if its still equipped since most 3.1 engines do have larger injectors and can easily have faulty injector ontop of them drawing just a little more power. but DO NOT replace the fuse with a higher rating whatever you do.
Raydar SEP 09, 11:24 AM

quote
Originally posted by danahart:

Thanks and that makes sense. Can I unplug the injector harness without taking off the manifold? Is the connector accessible or does the manifold have to come off?




It is quite accessible, just looking at the top of the engine - usually between the upper intake and the thermostat cap. No need to take off any manifold/mechanical parts, unless you want to unplug the connectors from the individual injectors.
It's usually a flat connector about 1.75-2" square. One half of the connector goes to the main harness, and the other goes to a handful of wires that disappear under the upper intake and connect to the injectors.
I said "usually", because some of the 88s had a different connector that was more of a cube shape, but performed exactly the same function. It will also be in about the same place.