250K+ miles. CA emissions car. No 25-AMP fuse under hood. Was a stick shift; converted to AT 5+ years ago.

Driven intermittently for the past 2-3 years. Always started and ran OK. Then
1. No start ~6 months ago. Owner replaced fuel pump relay w/ a spare; started right up; ran well
2. Same thing happened twice more ~ 10 days apart
3. No start ~ 2 months ago. Owner pulled MAS connector; still no start; plugged it back in and started right up.
4. Started and ran fine for ~ 2 weeks.
5. Then parked for ~ 3 weeks.
6. No start.

Now: No spark from coil. No 12V at orange wire on MAS w/ ignition on Both sides of coil show 12V (orange MAS wire ref https://www.brickboard.com/RWD/volvo/1575746/220/240/260/280/1990_volvo_240_dl_wagon_start_spark.html )

Notes
1. Has a tach. Only work owner remembers doing is pulling the instrument cluster to replace the temp gauge.
2. Timing belt is new; distributor turns
3. No click when fuel-pump relay is replaced, ignition on
4. Main fuel pump runs when jumped at fuse block

Replaced
1. Fuel pump relay
2. CPS (already had a new one)
3. Power stage module
4. Main CPU and ignition control w/ used units out of a running car. Had a 572 I think; replaced with a 951
5. Coil and Coil wire

I suspect a broken wire inside the harness. Perhaps near the MAS as jiggling that worked once.


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240 drivers / parts cars - JH, Ohio

Jon_H,

There is 25 Amp fuse, you just need to know where to look.

Use this URL to help.

http://cleanflametrap.com/emfuse.html

Since your car is a 91' and was a manual, it has or had the LH3.1 not the LH2.4, so things are a little different.

The two things that differ from 3.1 to 2.4 are MAF, and TPS.

Now don't quote me here, but I've heard that unplugging and plugging the MAF while the battery is still connected can fry it. I've also heard that there is no LIMP home mode on the LH3.1 when unplugging the MAF.

If I was you, I would swap back in the original ECU as that is what the engine wants to see to get it to run. Then I would find the 25 amp fuse and determine whether or not the fuse is blown. My suspicion is that it is blown, thus the reason you do not have voltage at the MAF or the Coil.

Let us know how you make out.

Matt

Thank you for the reply and link to Art B's page.

This car is a 2.4 - not all stick-shift >= 1989 had the 3.1.

"1989-1993 Bosch LH 2.4 - MAF sensor Bosch numbers: 0280212016, 0986280101 -
Black Plastic MAF housing w/ 6 pin plug"

The coil has 12V on both sides.

The original CPU is back in the car.

There is no 25-amp fuse under the hood attached to the battery.* Fuse-6 tested OK but the wire from it - or an inline connector - could be bad.

https://www.ipdusa.com/techtips/10087/how-can-i-tell-which-version-of-bosch-lh-fuel-injection-is-on-my-volvo-240

*Art's page: "However, in 1991, the engine and main cabin harness underwent big changes, moving this fuse out of the weather being among them. And since 1989, with LH2.4/EZK, the ignition computer was added to the circuit, not that it greatly affected load, but it did add some complication to diagnosis. Now that these cars are all in their twenties, this new location is another kind of problem. It is exposed to the moisture from leaky windshields and water following the harness down to the lowest point - the fuse panel."
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240 drivers / parts cars - JH, Ohio

Not having juice on that orange AMM wire is a big clue, but several problems can intervene to cause that.

1) The circuit through fuse 6 to relay terminal 30 can be open somewhere. Common place is at the end of the fuse itself, but also the connector pins at the black junction box on the fender, or on the fuse holder tabs might have trouble. From the fuse holder across the dash to the relay, there's a cabin-to-engine harness connector to offer trouble.

2) The relay itself or its socket.

3) The circuit which energizes the relay coil. The power for that comes from that same circuit powering relay terminal 30, but the ground is switched by the ECU yellow/black wire, which in turn needs power from the key switch blue wire to pin 35. If that is missing, a clue appears at the OBD test box: the LED won't come on at all in either test mode.


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Art Benstein near Baltimore

A truly happy person is one who can enjoy the scenery on a detour.

Art: thanks much for your thorough reply. It reminded me to recheck everything. I cleaned - again, but more carefully - the fuse-6 terminal ends and replaced the (steel) fuse with a new brass one.

I still lost connectivity on the RH side of the fuse when I rotated fuse-6. I recleaned and rescraped the terminal ends and made sure there was clean metal. The car started right away.

I should have known it was a problem w/ fuse-6 (or related wiring) when I had no 12V on the MAS terminal wire (which I lear5ned about from you) and the fuel-pump relay didn't click.

The fail was lack of due diligence (carelessness) on my part. Something like this:

1. When the owner had the problem I suggested he check and clean the main 25-amp fuse. This was my own car 10+ years ago but I didn't remember where the fuse was.

1a. He cleaned the fuse-block and fuses. (as I do - with a wire brush and solvent).

2. When I got the car after the final no-start, I cleaned the fuse block. But did a half-hearted job as he'd already done that.

3. I think what happened was: I'd find 12V on the right side of fuse-6; I'd turn the engine over with the key and the galvanic corrosion would short out fuse-6; I'd recheck and roll it out of habit and have 12V again.

3a. Compounding it was an intermittent fail of my test light - loose wire at alligator clip end that I resoldered late last night.

4. I also pulled the wires off the fastons on fuse-6 right-hand-side and cleaned the male and female ends.

Net, I should have 1st pulled all fuses and thoroughly cleaned the fuses and terminal ends. And replaced fuse-6 w/ copper/brass.

Thank you again for your clear thinking.

(My 1st test on a no-start is to pull the fuel-pump relay and listen for a click when I plug it back in (key on). I should have known from the no-click that power wasn't getting to it).
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240 drivers / parts cars - JH, Ohio

Great news and feedback!

"3. I think what happened was: I'd find 12V on the right side of fuse-6; I'd turn the engine over with the key and the galvanic corrosion would short out fuse-6; I'd recheck and roll it out of habit and have 12V again."

This is the same as I run into. The galvanic corrosion is a semi-conductor which easily passes enough current to light an LED or even a small incandescent test light, much less a multimeter, but has too much resistance to power the whole of engine management.

So, yes, the test light says it should work, but then you turn the key and it fails.

That's the reason for recommending the test light be probed at the orange wire on the AMM, because that indicates power is passing under load.

Brass or copper fuses have fixed this issue for me in every case.

"3a. Compounding it was an intermittent fail of my test light - loose wire at alligator clip end that I resoldered late last night."

I've used a piezo buzzer in place of a test light. I've wired it with alligator clips so I can attach it in a stable manner and not have to be within sight of the indicator while activating the circuit being tested. I'd be happy to put one in the mail to you for a SASE if you contact me. Email is on my web page.




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Art Benstein near Baltimore

They say you can do anything in international waters.
That's why I filled my hot tub with international water.

I have the same corrosion problem with battery cables: I have then on not-tight when I'm working on a car and have them on-off-on-off-..... and sometimes when the starter draws a load it loses the cable connection.

Most of my own cars have the brass/copper fuses but once they're out of my hands things change.

The probe at the orange wire is a great trick. It's one of the tips I keep in the manuals drawer of my toolbox.

I'll take you up on that buzzer. I'll email you. Great idea; hadn't occurred to me.
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240 drivers / parts cars - JH, Ohio

Thought I'd share one more way that piezo buzzer of yours can be put to good use.

Ever been annoyed by the back-and-forth needed when making adjustments to the tail lights to fix a bulb-out warning? You have to keep the motor running in order for the Bulb Failure Warning Sensor (BFWS) to operate, and you can't see it from the position you're in wiggling bulb sockets at the rear of the car.

Here's how I attacked an intermittent BFWS lamp today. The lamp would come on about 50% of the times I'd step on the brake, making it difficult to know whether I'd fixed it. I was pretty sure it was the left tail light, as I'd made the light go out by slapping it before. The part I don't care for, is removing the spare tire to get at it, and reconnecting the strap holding the spare in place afterward.

Today I set out to find the trouble with the piezo buzzer in hand. First, I disconnected the D+ wire from the alt, which then allows the BFWS lamp to operate without running the engine, just having the key in KP-II.



Then I made the orange can BFWS accessible (need to remove knee bolster in airbag cars) and connected the piezo buzzer between the K-terminal and a 12V battery source (fuse 12 was handy). Turned the key on, and blocked the brake pedal.





Lucky today, the trouble presented itself right away, causing the buzzer to squeal while I made access to the sedan's tail light. I'd thought the issue was at the bulb socket, as it often is, but this time I found the harness connector was where the balky connection was occurring. The buzzer would stop when I wiggled the harness plug. Elapsed time about 10 minutes, most of which was getting to the tail light.

A couple special tools (buzzer and brake pedal stick) made a big help and swift job of a very common trouble.
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Art Benstein near Baltimore

"I've learned more from my kids than they ever learned from me."