I've run through the diagnostics in the Bentley, and the only code I got was for the AMM (1-2-1). The heated wire test returned a value of 79 Ohms vs. the 2.5-4.0 specified in the manual. Is this value consistent with the failures experienced by others? I don't want to order something I don't need.

Symptoms were as follows:

Car would start and run very roughly with a strong smell of unburnt fuel in the exhaust. Fuel injectors are all ticking away, and the rough running was not due to one particular cylinder, as I could pull spark plug leads one at a time without making much of a difference to the "running".

FWIW, I'd originally replaced rotor, cap, plugs, and plug wires thinking problem may have been there, and did not know when those parts had been replaced previously.

Sometimes, the car would smooth out and run fine, but that happened less and less frequently until it reached the current state of not starting at all. On the final drive, the car was barely running, and would bog down or stall whenever I tried to accelerate.

I hope I'm on the right track, and the budget is very tight, so I thought I'd check in before proceeding.

Thanks.

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Brent in Chilliwack, BC, Canada

More than likely a better AMM will fix it.

With fouled plugs, just clean them with a wire brush and they will be fine again. The burned gasoline on the plugs will come right off.

You are compounding the problem. The additional fuel in each cylinder is washing your cylinder walls and rings, lowering your compression ratio and makes it harder to start and keep running. You have fuel, too much of it, and not enough air to mix it so it will burn.

Check the oil level. It is probably a little above the full line and is mixed with gasoline after all of these start attempts. You might want to change the oil after you get a new AMM.

Klaus
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Proud owner of a 220S. If I had more room, I would have more Volvos.

The car will start with MAF unplugged but will run poorly. Disconnect it and see if it then starts, if yes you have nailed the cause. Do not plug/unplug with key on.
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David Hunter

Just to clarify a bit the engine should start and idle fine with the AMM disconnected, it will drive poorly.
Dan

It coughed and wheezed, but wouldn't start (AMM unplugged). Not much life in the battery, so I'm charging it up and will try again tomorrow, but I'm getting the feeling that unplugging the AMM isn't making a difference.
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GSP in Chilliwack, BC, Canada

Speedo now jumps around when cranking the engine--that's new.

Also, "upshift" light flashes whenever car manages to run (related to not running properly on all cylinders?).
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GSP in Chilliwack, BC, Canada

Check for codes on the OBD module. THese engines need a good charged battery to run right.
Dan

Engine will crank for quite a few tries before the battery dies out, so I don't think that would be a significant problem.

The only code is 1-2-1 (AMM). Unfortunately, unplugging the AMM doesn't make any difference to the starting--just fires a few times and dies.

FPR vacuum hose does have a slight smell of gas, but if I remove the vacuum hose, fuel doesn't come out of the FPR when the engine is cranked. When the car was (barely) running, removing the vacuum hose from the FPR didn't affect the way it ran.
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GSP in Chilliwack, BC, Canada

"The only code is 1-2-1 (AMM). Unfortunately, unplugging the AMM doesn't make any difference to the starting--just fires a few times and dies."

This sounds exactly like the symptoms my 91 245 had with a bad AMM. I put a new AMM in and it started right away.

Does your 90 have the LH 3.1 fuel system?

The LH 3.1 system will NOT run with a bad air mass meter, contrary to earlier 240's.

Check the AMM #. If it is Bosch 0280217001 then you're looking at a $450+ part.
Very very hard part to find used.

Good luck.

Vin and AMM part # indicate 2.4.

I'm going to play around with it some more this afternoon. The strong fuel smell always had me believing that the engine was getting too much fuel, but I'm going to take a closer look at the pump.
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GSP in Chilliwack, BC, Canada

2.4 system is a good thing. Easier/cheaper to find an AMM if needed.

Don't forget to clear the OBD settings, crank it and see what the new settings are every once in awhile.

And wait for a solid charge to build up. I agree with Dan that you need the voltage for the engine to run right.

Latest update:

There is definitely spark--plugs spark when grounded against cylinder head. Plugs are quite black for being relatively new.

The car continues to stutter when I try to start it--today it actually ran (barely!) for about 10 seconds.

Tried pinching off fuel return line--still no start.

Main fuel pump makes a brief noise when turning on ignition ( I assume this is OK, as it would build pressure in system).

Jumping fuse 6 to fuse 4 runs the pump, although I can't hear anything at the tank, so suspect that tank pump may not be working. If I jump these fuses while cranking car, still no start.

Removing fuse 4 and jumping from left of fuse 6 to right of fuse 4 results in nothing happening--I understand this to mean the tank pump has failed, or not getting power.

I thought the car would run with just the main pump? I cannot get the fuel line separated from the fuel rail to test for fuel, but there is obviously at least some getting to the engine if it will fire (even just a little). If there is a secret to separating these fittings, please let me know!

At this point, I'm thinking that the main pump is likely worn out, and unable to compensate for the tank pump not running. When I had the car looked over by a Volvo shop when I bought it, he indicated that main pump was likely original (car has over 300,000km).

What puzzles me is the strong smell of unburnt fuel that was in the exhaust prior to the car failing to start--I thought it was drowning in fuel, but maybe that has just set me off in the wrong direction.



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GSP in Chilliwack, BC, Canada

A couple suggestions relating to fuel pumps;

Did you try the audio test for the tank pump?
Jump the fuses then go back and try to hear the tank pump running.

And I would give another try to removing the fuel line. Better to do the test before buying any new pumps. Try some pliers on the hose to get it rotating on the rail pipe before trying to pull it off, i.e. get the hose lose and moving then out and off.

I'm not sure how to test the pressure regulator. But after the pumps you've got the regulator then injectors.
Maybe it is time to have the injectors cleaned?
I'm assuming the filter is OK.

Black plugs? Maybe a new set would help. They're cheap.

Also, as stated before, clear the OBD and see what the reading is. If AMM code still shows up after each cranking then maybe it is the AMM.

A LH 2.4 used AMM is not that pricey and would be good to both test your problem and have as a backup...

I erased the fault codes, and after some more cranking, the AMM fault doesn't come up. However, I re-checked the resistance across terminals 2 and 3, and got the same 79-80 Ohms that puts it waaaaay out of spec.

I pulled the return hose off just aft of the FPR, and got fuel out of there when cranking, so fuel is definitely being pumped, and at significant enough pressure to that it makes it to the return line.

So, I've got fuel, spark, but it won't start, other than the occasional cough.

AMM doesn't test well, but fault code no longer appears. Unplugging AMM doesn't help.

Remember, prior to this consistent no-start, car would run well on occasion, though less-and-less frequently. Timing belt and tensioner are fairly new, so I don't see the belt slippiing and screwing up the timing, as that would not be an intermittent problem. I'm still wondering if it could be too much fuel, but what would have caused such a problem on an intermittent, and now permanent, basis? I wouldn't expect the injectors to allow excess fuel one minute, and then the right amount the next.
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GSP in Chilliwack, BC, Canada

I would check timing marks to make sure everything is correct.

New or cleaned spark plugs may be in order. Do you have spark at the plugs?

Are the plugs wet?
Dan

Today, I finally found some more time to tinker. It ran, but barely at first. I was encouraged, so I kept it going--it wouldn't idle at first, and would stall if I took my foot off the gas, but it would re-start. It clearly isn't running on all cylinders at all times. Once it warmed up, the idle smoothed out somewhat--at this point, it appears to be running on three cylinders quite well (as a note: the upshift light has always flashed when the car is running roughly--whenever it isn't running steadily on all cylinders. Not sure if this clue is worth anything?). As it idled, I pulled the spark plug leads one-by-one. By this point, each lead pulled would cause the car to run more roughly--except #4. I pulled the plug and grounded it to the engine--there is spark there. Plug was not wet.

Should I test for compression in #4?

As for the AMM: AMM fault code has reappeared, so I will replace it, provided there isn't a more serious problem somewhere.

I feel like I'm right back where I started: car runs--very poorly at first, but slowly gets better. If I were to drive it for a while, I have to wonder if it would eventually clear up and run well on all cylinders for a time as it did on occasion prior to the persistent no-start.

Any other ideas?
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GSP in Chilliwack, BC, Canada

Remove and reconnect the connector for #4 fuel injector and spray some contact cleaner on it.

Next time you get the engine running put a large screw driver on injector #4 ad the handle on your temple, do you feel the injector clicking?
Gan

IT'S ALIVE!!

If I listened to the injectors, they were all "clicking" away--even #4. But...when I removed the electrical connection to #4 for cleaning, I found that the plastic "latching" mechanism broken in such a way that it can "seem" well-connected, but isn't necessarily so. So, while the injector might be clicking away, it isn't necessarily working.

I cleaned the contacts, re-attached the harness, made sure the connection was snug, and tried to start it. It started immediately, and settled into a perfectly smooth idle right away. I took it for a drive and it ran fine.

Here and there, the upshift light flashed as I was driving, so I know that I need a more permanent solution to snugging the harness to the injector.

It's hard to believe that this little problem could lead to the no-start that I had been experiencing.

Thanks to those that have helped. Due to a crazy schedule, I haven't had a solid block of time to devote to diagnosing problems with the car, and I've certainly found that a few tens of minutes here and there aren't conducive to a methodical approach to figuring out a problem.

Rolling again,

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GSP in Chilliwack, BC, Canada

I am not sure that one flaky injector connection would cause a no start. I have on occasion disconnected 1 or 2 injectors with minimal effect on engine, at least not like pulling off a plug wire. Remember that the fuel is squirted into the manifold from every injector at once and then sits there till the next intake stroke. The vaporized fuel mixtured can be "shared" across the manifold so one injector does not stop the engine.
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David Hunter

Congratulations, there should be a metal wire clip that keeps the connector attached to the injector. The connector body can be replaced but getting the pins out can be tricky.
Dan

Glad to hear you found the problem and didn't have to spring for some expensive unneeded part.

Bert

Yes but a known good spare AMM is one of the things everyone should have for trouble shooting and emergencies.
Dan

I'm not out of the woods yet--the car got me to work, but didn't get me home!

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GSP in Chilliwack, BC, Canada

You need a good well charged battery for starters. The ignition and fuel injection system will not work without it.
Dan

I can crank it to try starting it 8-10 times between charges before the battery is depleted to the point that you can hear the starter slow down.
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GSP in Chilliwack, BC, Canada

If the engine does not start after a few seconds of turning over you are wasting the battery.

Check for spark, pull a plug and check for gas.

The engine should start with the AMM disconnected if you have spark and fuel.

Dan

Seems rather hard to get around those figures of the AMM. You got to be sure you are on the right pins is my warning with the readings you are taking. You might be right as rain but the information on which pins may be misleading to exactly which AMM you are checking.

You might check the Fuel Pressure Regulator for gas in the vacuum line to the manifold. If it has ruptured, it may dump raw fuel into the engine. Might explain the fuel smell.

In limp mode it should not get that much gas but then again anything is possible if the ECU get the wrong or no information to run with.

Wait for more Bricksters, I'm sure they will have a better response.

Phil

have you tried unplugging the AMM and seeing how the car runs in Limp Home mode ??