93 940 Turbo/ 224k...

All signs seem to be pointing towards a bad ECU, but I want to be sure. The problems are cold start (cranks and sparks, but little fuel), cooling fan runs full-time, and am now hearing the fuel injector signals thru my radio. Each "pop" on the tuner coresponds to a stumble at the injectors. This consequently goes away when the ambient temp is warmer. The engine temp doesn't seem to matter.

I am getting a 123 code for the ECT. I replaced it with no change. I am getting over 6 volts (with car on) when I check it at the ECU connection in the foot well. I heard it shouldn't be more than 5. Also replaced the FPR, FIR (radio suppression), dist. cap/ rotor, and main fuel pump.

Is there a good way to test my ECU? It's a Jetronic 937, which I have seen very little info on in here.

You must have a ground that has opened up. Use the excelent information in a previous post to check it out.
--
'96 965 with 16' wheels at 121K. Had '85 745 Turbo Diesel for 200K.

Dear fullfathom,

May this find you well. Engine Control Module 0 280 000 937 (Bosch Part Number; the Volvo Part No. is 3547 781-0) was used in '92-'95 cars, with the B230FT engine.

This ECM having been used over three model years, it should not be that hard to find a replacement at a salvage yard. In a perfect world, you'd want one taken from a car that was/is known to have run smoothly.

It is best if you can find a yard with 940s, that allows you to remove the part you need. You plainly know how to get at the ECM. Just assure the yard owners, that you will remove parts carefully, and leave them in the front seat (or replace them were they were). In that way, they'll know that you won't damage saleable parts.

To test the ECM, you'll likely need to buy the relevant Volvo Technical Manual (see www.volvotechinfo.com) or an on-line equivalent (see www.alldata.com).

Hope this gets you started (pun intended) on the road back to smooth running.

Yours faithfully,

spook

thanks spook, I'll start the search. I'm still curious if a bad ground or shorted wire under the hood has caused the ECU (ECM) problem. I'm a little warry about puting in a new one, and frying that one too. I guess we'll see!

fullfathom

Dear fullfathom,

Good a.m. and may this find you well. The Volvo Tech Manual showing wiring diagrams for the 1993 940s (TP 32208/1), shows that for Bosch fuel management systems, the ECM is grounded to the engine, by a BLACK wire at position #17 on the ECM connector. The wire runs to position #6 on Connector C54 (below the strut housing bracket on the passenger side [US/Canada models]) and thence (so it appears) to the rear fuel rail support bracket, which is atop the intake manifold.

The ECM's signal ground also runs to the engine. This is a BROWN wire, that runs from position #5 on the ECM connector. The wire runs to position 8 on Connector C55 (below the strut housing bracket on the passenger side [US/Canada models]) and thence (so it appears) to the the forward fuel rail support bracket (or something very close to it), which is atop the intake manifold.

For cars with the Rex/Regina fuel management system, the ECM power ground is a BLACK wire at position #19 on the ECM connector, which runs via position 5 on Connector C55, to the same place as noted above (rear fuel rail support bracket). The ECM signal ground is a BROWN wire at position #5 on the ECM connector, which runs via position 8 on Connector C55, to the same place as noted above (front fuel rail support bracket).

Hope this is helpful.

Yours faithfully,

spook

By the sound of it, I too suspect a bad ground. Taking the risk of stating the blantly obvious, I think I would check the battery ground and the engine grounding strap first. Grease, oil, dirt and the elements tend to degrade these very necessary items over time.