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Old 05-22-2020, 08:22 PM   #1
Fresh Air Inspector
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Default 1994 940 NA to Turbo Conversion - no start

Hello All,

Hopefully someone has dealt with this issue - my searches have not found any words of enlightenment.

After months of delay I finally reached the big day - firing up the transplanted engine only to be greeted with a 'no start'.

Background
The donor is a 05/1994 940 turbo (T) sedan and the recipient; a 02/1994 940 normally aspirated (NA) wagon. The ECU and EZ-K modules have been swapped so these are correct. Both cars were fully functional before I started the engine swap. No wiring changes were made other than moving the battery (new feed to the started motor), moving the MAF from the drivers side to the passenger side and adding the pre-heater to the crankcase ventilation hose.

I've traced the problem down to a fuel injection issue. The Radio Interference Suppression Relay is energizing but Fuse 11 is not providing 12V to the fuel injection relay,the O2 sensor or both fuel pumps. Fuse is OK, meter shows 0V with ignition on, same in start mode.

Analysis
The NA engine circuits use a 4 pin relay for the fuel injection whereas the T engine uses a 6 pin (basically 2 relays in one housing). The NA relay panel does NOT have any electrical connections available for this 6 pin relay. The major issues as I see it are as follows;

ECU - pin 9 connects to;
NA; MAF sensor pin 5
T; Air Preheating – pin 1 + Idle Air Control valve – pin 1 + Fuel Injection Relay – pin 1

ECU - pin 20 connects to;
NA; Fuel Injection Relay pin 4
T; Fuel Injection Relay – pin 2

ECU - pin 21 connects to;
NA; Radio Interference Suppression Relay – pin 1
T; Fuel Injection Relay – pin 4

Hopefully I haven't damaged the ECU trying to start the car.

Does anyone have any ideas or suggestions??? This one has become quite a challenge.
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Thank you and take care,
PK
1971 VW Beetle Cabriolet, 1994 Ford Escort, 1994 940 T Sedan, 1994 940 NA Wagon

Last edited by Fresh Air Inspector; 05-25-2020 at 04:54 PM..
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Old 05-22-2020, 10:22 PM   #2
apachechef
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resistor pack or did you use high impedence injectors?
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Old 05-23-2020, 02:30 AM   #3
JW240
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The na 940 already was LH, right? Then it should have the white 6 pin FI relay..
If you start it without resistor pack you can/will burn out the injector driver transistor, which is a bummer but luckily a very cheap part, just need to replace it on the ecu pcb, which requires soldering.
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Old 05-23-2020, 02:47 PM   #4
2manyturbos
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Quote:
Originally Posted by JW240 View Post
The na 940 already was LH, right? Then it should have the white 6 pin FI relay..
If you start it without resistor pack you can/will burn out the injector driver transistor, which is a bummer but luckily a very cheap part, just need to replace it on the ecu pcb, which requires soldering.
Some of the late NA 940s use the four pin relay he describes. The 1994 940 NA I have at my shop has LH 2.4 injection and the 4 pin relay.
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Old 05-23-2020, 03:44 PM   #5
JW240
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Quote:
Originally Posted by 2manyturbos View Post
Some of the late NA 940s use the four pin relay he describes. The 1994 940 NA I have at my shop has LH 2.4 injection and the 4 pin relay.
OK, I was not aware of this. Thnx!
Thought of the radio suppression relay instead.
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Old 05-23-2020, 05:10 PM   #6
Fresh Air Inspector
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Hello All,

Appreciate the responses.

Apachechef - I used high impedance fuel injectors.

JW240 - no 6 pin white relay in position E (relay board). In fact the socket is not wired. I only have the Radio Suppression relay on the passenger inner fender and a Fuel Pump relay in position M on the relay board. Have no idea where the Fuel Injection Relay is located unless what the Mitchell wiring diagram calls the 'Fuel Injection Relay' is the 'Fuel Pump Relay' as the wiring for both pumps goes through that relay.

2manyturbos - thanks for the confirmation. My Mitchell wiring diagrams also show a 6 pin for the turbo and a 4 pin for the NA. However, I have yet to find the 4 pin 'Fuel Injection Relay' indicated in the wiring diagram. Any ideas where Volvo might have hidden it?? Unless it is the 'Fuel Pump Relay' as mentioned in my comments to JW240.

Today (Sat), I was too discouraged to work on it. Tomorrow I will do some detailed investigation to see if I can find a potential solution. My gut tells me it is linked to the '6 pin relay' versus the '4 pin'. I have a spare 6 pin relay and socket if I have to modify the wiring harness.

Having said all that I am always open to any feedback and of you may have.
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Old 05-25-2020, 04:53 PM   #7
Fresh Air Inspector
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Default 1994 940 NA to Turbo Conversion - no start - SOLVED!! :-)

Hello All,

YES - it is running and no leaks or unwanted noises. :-)

After a number of hours reviewing wiring diagrams, testing connections and measuring on Sunday I found that fuse 1 (25A) that supplies 12V to the ECU, EZ-K and fuel pump relay was not live. The Mitchell wiring diagrams were confusing as it appears that fuses 1 through 4 share the same buss from the battery (via to red wires). Not the case, each fuse has it's own feed and number 1 uses a brown wire.

Turns out when I was moving the battery and the feed wires from the passenger side (940 NA), to the drivers side (940 T), the brown feed wire to fuse 1 was not connected properly. Can't believe I made such a stupid mistake, feel like a right git, as the Brits say.

Still need to bleed the brakes and finish a few minor items before a test drive and final tweaks.

Once again, thanks to those of you that took the time to read my opening message and responding.
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Old 05-25-2020, 04:59 PM   #8
JW240
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Good diagnostics and happy to hear it runs now!
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