Here is where I stand with the 94 n/a manual transmission 850 that won't start:

1. I have verified I have fuel and spark to the engine.

2. I removed the camshaft position sensor from my 98 s70, put it on my 850, still nothing.

3. I swamped ignition coils from the s70, still nothing.

Is there a way I can test the ECU to ensure its working? When I took the top off the box I see 2 cartridges. Which one is the ECU and what does the other 1 do?
Could it be the temp sensor or the crankshaft sensor? I'll be checking compression on each cylinder tonight. Thanks for all your help.

Eddie G

5 speed. I was going to finally have it towed to the dealer but I decided to push it out of the garage and to my down hill driveway to see if it would bump start. It did and has been running fine since. I could only thing that something jammed and was letting too much air into the engine for it to start via the starter.

I like to keep a spare set of relays, cam sensor, maf sensor in the garage for testing. ECM's are a dime a dozen on eBay. I might add that to the collection. You might too.

Be sure to disconnect the battery b4 pulling an ECM.

One of the units is labled Bosh LH3.2 for fuel injection, the other is the ECU. Be careful removing and inserting them.

Klaus
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Did you do your Random Act of Kindness today?

The other control unit is for the ignition system since you have a manual trans.

you say you verified fuel and spark, which is good. Did you verify that you have proper pressure as well as merely fuel presence? You will need pretty decent pressure for the fuel injectors to work - I think it's something like 35+ PSI before they will even work. You might be able to verify that number by searching around the board a bit.

Clean your throttle body with a toothbrush and throttle body cleaner.

Clean your IAC with throttle body cleaner - just spray a bunch of cleaner in, plug the holes with your fingers, shake it around, empty, repeat a few times.

Make sure your CPS wiring is not near the ignition wires as this can sometimes cause interference.

There should be nothing wrong with your ECU unless you've been playing with the electrical system, like plugging/unplugging components with the engine running, jump starting recently, etc.

BTW the control unit with the Bosch sticker is the engine control unit, the other one is for the transmission.

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1998 V70 AWD->FWD->AWD Turbo 220k+

Which box is the ECU? Is it the driver side or the passenger side?

Eddie G

Passenger side. It has a fresh air vent going to it.

What are the compression readings?

The ECT sensor will not prevent a start, just run rich. Unless the plugs are fouled up.
Running rich will wash the rings with gasoline during start attempts and lower compression readings. If compression is low on all cylinders, add a tablespoon of oil to each piston and do the test again. If the compression comes up to 175+ on all, put in the plugs and try a start.

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Did you do your Random Act of Kindness today?

Klaus,

I'll test the compression tonight. I know its on the passenger side, but within the box there are 2 units. Which is the ECU? Is it the 1 on the left or right?

Eddie G

Hi, as Klaus has said it's the right side/passenger side.

JR

2 thoughts:
1) My 93 850 Auto had multiple non-start issues. The first one was a break in the wiring harness while I was in college. The second involved a pressure switch in the ignition, kind of a predecessor to today's "smart" keys. I sold mine a few years ago, so I'm going by memory here. Remove the clam shell around the steering column and pull the ignition cylinder out, clean all the electrical contacts with contact cleaner (radio shack) and reassemble.

Secondly...I don't know if Volvo has one, but my Acura has a clutch sensor to ensure the clutch is engaged in order to start the car. If Volvo used one in yours, did you check this?

Jon

Jon,

Thanks for the response. did your 93 crank when you had the issue with the key? Mine cranks just won't start. Also, where was the break in the wiring harness on your 93. Sounds like something I should look at.

Eddie G