Kernow90 · Mar 10, 2016

Evening folks,

Ive just swapped out my 3.5 su v8 for a 1988 rrc 3.9 efi, having a few issues getting it to run,
I have fuel and have spark and continuity from the -v on coil to the ecu, but the injectors wont fire.

Ive attatched all relevent ground wires from the ecu ( that have been labelled ground on diagrams found online and manuals) and have the two black earthe wires to the back of the head not to mention to main earth straps from block to the chassis.

Can anyone shed some light on what i might be missing, i have 12v to the injectors but they just wont fire ( i know theyre switched earth).

Any help would be fantastic as i dont have a lot of hair left after oulling it out with teying to get it running haha

MattMatt · Mar 11, 2016

Have you checked the ECU and the continuity of the wiring? There is a few tests you can run by just using multimeter. I've attached a file that may be useful

Kernow90 · Mar 11, 2016

Only ones ive chacked is the pickup from the coil -ve and the earthes not sure how to test the others but will have a look at the file so frustrating!

cooltide · Mar 11, 2016

Did you change from points type coil?

Kernow90 · Mar 11, 2016

I have the coil that came with the 3.9 and am using this,

Question for you electrical boffs, as i am going from an auto rrc v8 to a manual, ( using the original 3.5 manual gearbox)
Do i have to bypass the gear inhibitor switch and bypass the inetria switch? As i dont have these but am wondering if the ecu will still thinks they are there and is stopping it from firing? Going to have one last good look tomorrow before i just oay someone to come sort it, as much as id rather accomplish this conversion myself

discool · Mar 11, 2016

The selector inhibit switch will inhibit cranking only other than in P or N which is via a relay, although there is an ECU connection P and N positions which is earthed in the two positions, what the function of this connection I don't know.
All EFIs will have the fuel cut off inertia switch as a safety feature.
Does you coil still have one or both resistors attached on the negative side of the coil one is inline with the supply to the ECU as they are on the disco 3.9s.
U do have a permant poss supply to the coil when starting?

cooltide · Mar 12, 2016

discool said:
Does you coil still have one or both resistors attached on the negative side of the coil one is inline with the supply to the ECU as they are on the disco 3.9s.

Good point. The later looms incorporate the resistor as mine does from 1992 rrc. If it had a plastic resistor fitted to coil neg, it needs to be reused and ecu to coil wire plugged into it.
The inertia switch is inline between fuel pump relay and fuel pump so if you roll the car, gravity switches it and cuts fuel pump. If the fuel pump primes it is working.

Kernow90 · Mar 12, 2016

Mine has a small black resistor fitted near the ecu end and this is still plugged in, it also has the tune resistor ( the green one in the clear plastic shrink wrap bit) this is still fitted also.

Kernow90 · Mar 12, 2016

Although not sure which if any of these that i just mentioned as inline with the coil to ecu wire

discool · Mar 12, 2016

I don't expect the location of the resistor matters. I found them by accident strapped to the coil and gave them a clean, as I had nothing better to do, but that didn't make any difference.

One resistor is for coil to ECU the other is to a "trip computer-manual transmission so not for the 3.9 disco in the uk. Info shown in the Haynes disco WM
Are u using a RRc or disco wiring diagram ?
.

Kernow90 · Mar 14, 2016

Its alive!! Thank god. Found a earth missing for the ecu and the one wire into the coil had managed to break off but sit in just the right place to look like it was connected.

Although not the end of problems, ive gone from a auto box to the original manual that is in my defender, as far as i am aware i can just swap all the bits over on the clutch and it would work, is this correct?

Basicall i had a 3.5 SU v8 with a manual box,

Ive fitted a 3.9efi auto engine from a RRC

And kept my original manual box.

I took everything off the 3.5 and fitted it in exactly the same order to the 3.9 should work shouldnt it?

Cheers guys for all the help so far.

cooltide · Mar 14, 2016

@jamesmartin is best to explain

jamesmartin · Mar 14, 2016

Kernow90 said:
Its alive!! Thank god. Found a earth missing for the ecu and the one wire into the coil had managed to break off but sit in just the right place to look like it was connected.

Although not the end of problems, ive gone from a auto box to the original manual that is in my defender, as far as i am aware i can just swap all the bits over on the clutch and it would work, is this correct?

Basicall i had a 3.5 SU v8 with a manual box,

Ive fitted a 3.9efi auto engine from a RRC

And kept my original manual box.

I took everything off the 3.5 and fitted it in exactly the same order to the 3.9 should work shouldnt it?

Cheers guys for all the help so far.

yes you just swap over all the parts, plus fit a spigot bush (549911)in rear of crank,3.9 is a slightly stronger clutch but either fits as the rest is the same

cooltide · Mar 14, 2016

jamesmartin said:
yes you just swap over all the parts, plus fit a spigot bush (549911)in rear of crank,3.9 is a slightly stronger clutch but either fits as the rest is the same

Part no. too

Kernow90 · Mar 14, 2016

Ahhh ****, i think i may have missed out the bush, or did i, **** i cant remember haha, what will happen if i havent fitted it?

MattMatt · Mar 15, 2016

It won't do your g/b much good. The bush holds the first motion shaft inline while the the clutch is in. Not having one might destroy some bearings over time.

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