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Stumped and Frustrated: 3.9 V8 into a ROW 110

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110 v8
6K views 76 replies 19 participants last post by  85Red110 
#1 ·
Im going to shoot for the stars right off the bat, and ask if anyone has a wiring diagram (that a novice can understand) of the harness from a 3.9 V8, which will tell me what every plug and wire is for. I have searched everywhere online that I can think of, and all I have found are diagrams that dont match what I have in front of me, or diagrams that are not detailed enough. The engine/wiring harness came from an RRC, and there are multiple plugs and wires on it that I cant figure out. I also need to know where the harness/ECU gets power, and which wires connect to the ignition coil. I have fuel supplied to the injectors, and the engine turns over, but I have no spark.

I am completely stumped, and I am sure its because I am a rookie, so do me a huge favor and go ahead and treat me like I dont know anything, rather than assume Ive tried what you might consider to be obvious solutions. My level of frustration has reached epic levels, so I am throwing myself at the mercy of this forum for any and all help. :icon_peace:

I am sure I have left out some details that some of you might need to evaluate my problem, so dont hesitate to ask.

TIA,
Kent
 

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#2 ·
A LOT of stuff you will not need mate...the engine came out of a classic RR...it had electric seats, ride height adjustors, bunch of ECU stuff, A/C, etc etc - that you are not going to need. - why don't you just run the basics - coil, ignition, dizzy, battery, alternator and see what that gives you...should be able to get a spark at the spark plug?
 
#4 ·
Is your distributor in the correct location? Being a tooth or two out will cause the same symptoms, wanting to fire but just won't. Unless you are 100% sure that you aren't getting spark.
 
#5 ·
The ignition coil is not getting power. That white wire with black rings has no current. That's why I need to know how the harness gets power. Sorry if that seems like an amateur question, but I'm going off a knowledge of EFI engines that is elementary at best.
 
#7 ·
If spark is the problem, I'm confused about the problem. The ignition system has nothing to do with the EFI ECU. The ignition system is a couple of wires. You have power at the coil and to the correct side? the EFI system does not supply power to the coil. It just has a sense wire.
 
#22 ·
RRC's, at least up to '91, is solid white to positive coil... which makes me think his harness is '92-95 since it's white w black rings.

I can't read a schematic too well but I can poke around my engine & provide any pics you may need to aid in the correct hook up.
 
#23 ·
You have 4 wires going to the coil. 2 to positive and 2 to negative. What are each of the wires connected to?

there should be the correct switch power that stays on (white) to the positive. White/black should go from the negative to the distributor ignition module. Another white/black should go through a resistor to the EFI ECU. Beyond that, you might have a tach signal, which would be the negative as well.
 
#24 ·
I think your wires are mixed up on the coil. Your white w/ black rings should be negative.... if that's the one that runs to the ECU. Other neg to the distributor amp. One positive to distributor amp and the other to switch power.

That's how mine is wired except my neg to ECU is a white with black line not rings.
 
#26 ·
Ya the harness is actually a pretty nice one along with a known good ECU. Diz is timed properly (I did it myself) and the coil is connected the right way.
The issue is that the harness has a lot of unused wires. He is not sure what goes where and frankly I don't either without the proper literature at hand. I propose that we just simplify with a Megasquirt in fuel-only mode so he can start driving it. I have everything needed to get him on the road, just don't have two minutes back to back that I can get over to his place.
I will try to assemble an emergency start-up kit that will give him a running engine. In the meantime he can work on the gazillion other things he needs to do on that mule.
 
#32 ·
... the coil is connected the right way.
The ignition coil is not getting power. That white wire with black rings has no current.
From your pictures I still think you have two wires reversed on the coil. If the white with black rings goes into the harness with the MAF wiring then it's heading to the ECU & should be on the coil's neg side. Also pull the lower white wire you have the neg side & test it for power with the key on.
 
#28 ·
I thought you were further along than this. I could try come over one day after work and give you a hand, although I'm not sure I'm going to be that much help.

So did you keep all the existing wiring you had with the 2.8, or remove it and use everything from the RRC harness?

Does anyone know what the minimum wiring the ECU needs to be happy and function?

Have you hooked up a rover gauge to see what if anything the ECU thinks about it's current state?

Bill, so the peanut gallery can play along, what year is this harness/motor from?
 
#29 ·
Harness is from a 1993 LWB 4.2. It has a number of plugs. I can't recall what plugs in to what, so I can hop over to Rob's shop and get some pics of what goes where since there happens to be another 1993 LWB in the process of being taken apart ( sniff )
I think the major issues are where does the power come from/go to and which plug does what.
The Rave manual covers the 1995 models but nothing on line for the 1993-4. So i'm digging thru both my old manuals and online sources.
 
#33 ·
The white wire on the neg terminal is a ground wire. I had to use whatever wires I could find for this frankenstein trainwreck of an engine swap. I ran out of money a long time ago, and am scavenging for whatever scrap I can find....
 
#34 · (Edited)
Just a straight up ground... that wire should run to the ECU.
The white black should be your switch power... where does it run to?


If you want to simplify it with a 3.5 harness, I can pull one for you. I think I harvested two relay bases that could be rebuilt but may not be needed in your case. I think one was A/C.
 
#35 ·
The negative should not go to ground. One wire to the ignition module and another to the ECU via a resistor. If you ground the coil, how would the ignition module fire?
 
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