[solved] (LH2.4 240) 1993 Engine Loom to 1991 Dash Loom

wzrdovryndr · 2023-04-01T00:51:40+00:00

Short of finding another donor car to pull the harness from, I cannot see an easy way out of the predicament you're in

wzrdovryndr

Thanks for the wiring diagrams, I’ll have a look through and see if I can work out what needs to go where.

wzrdovryndr

Thanks to Dave’s Volvo Page, I’ve found what I think is the white plug on the donor engine harness I’ve discovered.

The ‘93 240’s had the wires from grey plug in the engine moved to a white 24 pin connector under the dash.

wzrdovryndr

Bit of an update:

1991 has a grey 8 pin connector in the engine bay against the firewall, and a black 14 pin connector in the passenger side footwell near the EZK. Both these connectors join the engine harness to the dash harness.

1993 has a white 24 pin connector in the passenger side footwell near the EZK.

As I discovered on Dave’s Volvo Page, the 1993 loom eliminated the grey connector in the engine bay and re-routed those wires to the white 24 pin connector.

I’ve compared the two wiring diagrams I linked earlier and have found only one main difference:

1991 Injector circuit has a thick orange wire.

1993 Injector circuit has a thick red-black wire.

I’ll trace each colour wire back to its corresponding sensor/relay to confirm that the diagrams I’m working with are correct, but each pin number and wire colour on the black 14 pin connector matches up with the 24 pin connector.

If that all checks out, I’lI unpin the black 14 pin connector and pull the 8 pin connector wires through the firewall in my wagon, take the dash harness side of the 24 pin connector from the donor and re-pin the wagon wires to match the late engine harness.

Pretty specific scenario, but I figure I’ll keep updating this thread in case someone else encounters the same thing.

Fingers crossed this works!

Major Ledfoot

The standardised ground connections are shown in the 240 factory-issued Green Books, TP-31767/1 (for 1991) and TP-32352/1 (for 1993). I have copies of both on the OTP 240 Green Book USB stick, but unfortunately can't do screenshots as LockLizard disables that function. You might get lucky by googling those TP numbers and find scanned PDFs of the Green Books.

JFTR, there appears to be two ground connections at the inlet manifold, according to the diagrams.

Ex850R

Major Ledfoot
The standardised ground connections are shown in the 240 factory-issued Green Books, TP-31767/1 (for 1991) and TP-32352/1 (for 1993). I have copies of both on the OTP 240 Green Book USB stick, but unfortunately can't do screenshots as LockLizard disables that function. You might get lucky by googling those TP numbers and find scanned PDFs of the Green Books.
JFTR, there appears to be two ground connections at the inlet manifold, according to the diagrams.

Take photo of screen?

wzrdovryndr

Major Ledfoot
The standardised ground connections are shown in the 240 factory-issued Green Books, TP-31767/1 (for 1991) and TP-32352/1 (for 1993). I have copies of both on the OTP 240 Green Book USB stick, but unfortunately can't do screenshots as LockLizard disables that function. You might get lucky by googling those TP numbers and find scanned PDFs of the Green Books.
JFTR, there appears to be two ground connections at the inlet manifold, according to the diagrams.

I was able to find the 1993 TP-32352/1 diagram, but found the two diagrams that @Slowbrick linked worked much better for me.

Major Ledfoot

^ Poor resolution makes that a waste of time for an electrical diagram.

wzrdovryndr

Pulled the wires from the engine bay through the firewall and pinned everything into the new style 24 pin plug. I still need to tidy up and re-wrap the harness but waiting until I know everything is OK. I had to solder on the pins from the donor dash loom so I had male pins.

Cranks but won’t fire, currently have no spark but power to the coil.

That’s as far as I could get today!

EDIT: Can’t figure out how to remove the double up image on my iPhone.

wzrdovryndr

Fixed a couple of pins that hadn’t clicked into the connector properly, also discovered I hadn’t connected the power stage somehow.. facepalm

Despite this, I still have no spark.

I have power to the injectors, I still need to check pulse.

I have power to both both terminals on ignition coil, but it appears I have no ignition pulse. I checked this by placing a test light between the + and - terminals and observed while cranking.

I’ve tested the crank angle sensor and had around 160 ohms of resistance which I think is fine.

Not sure where to go from here to find where this start signal is lost.. any suggestions?

ramrod

Re-check all connectors

Especially the RPM sensor (male and female pins)

Ignition power stage, as well as all other plugs and relays

Does your car have a radio suppression relay? If so the injectors are powered by it

wzrdovryndr

ramrod
Re-check all connectors
Especially the RPM sensor (male and female pins)
Ignition power stage, as well as all other plugs and relays
Does your car have a radio suppression relay? If so the injectors are powered by it

The rubber shielding has broken down on the RPM sensor (crank position sensor I’m assuming), exposing the foil shielding. Not sure if that would be causing any issues.. I think I might replace it anyway instead of trying to fix it.

AFAIK none of the 240s had a radio suppression relay.

Next time I’ll re-check all connectors again as it’s possible I’ve missed more.

Something I did find though, I have a total of 3 blue and 3 red-white wires at the coil. Schematics show 1 blue to the power stage, 1 to ignition switch, 1 red-white to power stage and 1 to tacho. The remaining blue and red-white wires have been cut, and I can’t find where they go.

ramrod

I believe the coil and starter motor need to be connected together

wzrdovryndr

ramrod
I believe the coil and starter motor need to be connected together

I don’t think so, there is no link I can see in the wiring diagrams.

carnut222

Is the insulation on that blue coil wire running under the mounting bracket cut? It's not grounding out on the bracket is it?

wzrdovryndr

carnut222
Is the insulation on that blue coil wire running under the mounting bracket cut? It's not grounding out on the bracket is it?

it looks like it in the photo, but I’m actually holding the two cut wires in my hand when taking the photo. They’ve been taped up for now so they’re not earthing out.

Edit: I zoomed in and I see what you mean now.. I might have to double check that. Good spotting!

ramrod

Silly me, was thinking of the k-jet cars.

forgot the ecu makes the connection with lh2.4

wzrdovryndr

@carnut222 Good spotting! Not sure how I missed that damaged wire..

I’ve repaired the damaged wire and I’ve ordered a new crank angle sensor from PAT (CAS-107).

When I have some more time I’ll verify switched and constant power at the EZK; Pin #5 (RED constant) and Pin #6 (BLUE ignition switched).

Once the new CAS is here, I’ll work my way back from the coil starting at the power stage, checking for start pulse.

I also need to spend some time learning how to use the diagnostic port.

wzrdovryndr

I think I’ve found my problem - no constant 12V to the EZK!

I went back to the wiring diagrams I have been following and found there are different sources of constant 12v between years, one being engine bay and one being fuse #6.

I’ll route constant 12v from fuse #6 to the EZK via my 24 pin and fingers crossed that’s my only issue. I have power after the fuse, and I know I have power to my ECU and fuel pumps are working, so I must have cut off the EZK from power somehow as they were originally powered on the same circuit.

carnut222

wzrdovryndr
I think I’ve found my problem - no constant 12V to the EZK!
I went back to the wiring diagrams I have been following and found there are different sources of constant 12v between years, one being engine bay and one being fuse #6.
I’ll route constant 12v from fuse #6 to the EZK via my 24 pin and fingers crossed that’s my only issue. I have power after the fuse, and I know I have power to my ECU and fuel pumps are working, so I must have cut off the EZK from power somehow as they were originally powered on the same circuit.

One thing I found when I converted my 79 245 to LH2.4 using a complete 93 harness is the ignition switch pin-outs are different for the early and late (I think 1990-later) ignition switch. So after I did the conversion, I discovered I had no power to the ECU (or EZK - can't recall) when cranking (or maybe when the ignition was in the on position but not cranking). Once I figured that out and swapped the correct late ignition switch in, the car fired right up. Not saying it has anythign to do with your problem but it might for some reason. In theory all should be OK as the 91 and 93 use the same ignition switch.

wzrdovryndr

carnut222
https://ozvolvo.org/discussion/comment/217271#Comment_217271
One thing I found when I converted my 79 245 to LH2.4 using a complete 93 harness is the ignition switch pin-outs are different for the early and late (I think 1990-later) ignition switch. So after I did the conversion, I discovered I had no power to the ECU (or EZK - can't recall) when cranking (or maybe when the ignition was in the on position but not cranking). Once I figured that out and swapped the correct late ignition switch in, the car fired right up. Not saying it has anythign to do with your problem but it might for some reason. In theory all should be OK as the 91 and 93 use the same ignition switch.

Hmm, interesting. I haven’t checked ignition power to the EZK yet.

I was checking continuity of the constant power wire from fuse #6 to the EZK, when I discovered that I also have continuity to ground.

I disconnected the EZK, ECU and 24 pin connector to isolate the engine loom from the dash loom. Checked the red constant power wires in engine loom, no short to ground. Checked the red constant power wires in the dash loom and had continuity to ground.

Unless I’m misunderstood, I have a short to ground somewhere in the dash loom, which I haven’t touched other than soldering on the pins for the 24 pin connector.

This wagon was running 12 months ago before I pulled the engine, so I know there were no prior issues. I visually inspected the dash loom where is runs out and along the firewall to the drivers side of the engine bay, in case I’d crushed the loom when dropping the engine but there isn’t any visible damage.

I feel I’m going deeper and deeper into this rabbit hole and over complication the **** out of it.

PS: Fuse #6 isn’t blown, I don’t know how the loom hasn’t caught on fire and popped fuses with power shorted to ground.