No air mass meters in St Louis stores or dealers. Will check junk yards. What is wiring code of AMM harness plug?

 

I noticed that the Red/Green wire on pin #3 of the radio suppression relay goes to the ballast resistor. Could a failing ballast resistor be sensitive to heat thus breaking the ignition circuit causing my problem? Seems like an inexpensive part to carry and then install when the next "flame out" occurs. What say ye? TD

 

the ballast resistors are in series with the fuel injectors on turbos, because the higher flow injectors were too low impedance to connect directly to 12V.

those resistors are very simple and rugged, its highly unlikely to be anything wrong with them.

 

It also mentions that RSR pins#3 & 4 may be temporarily bridged to bypass the relay. Seems like this would be good to try at the next flame out? Should that enable us to start again, how long could we drive like that to get out of a precarious situation? Yesterday I got stranded in Saint Louis rush hour traffic and had to be pushed to safety by the police and then towed back to out base here.

 

you could drive all day, just remove the jumper when you shut it down.

 

Thanks Pierce. We leave SL today for Nashville. Replaced the fuel pump yesterday I installed in Pocatello last Wed and will be selling it back to O'Riellys as it just was way to noisy for me and given the shoddy assembly on the first one from that company that leaked like a sieve, it made me nervous and there was no better place than here to do it. Also inspected & cleaned the air mass meter and the connector. All looked well there but I may have one shipped to one of our future destinations. Have you ever dealt with Parts Geek on line? I've installed wire taps to jump those wires at the RSR and am carrying a fuel pressure regulator as well. Sounds like those ballast resistors are not the likely culprit and I would imagine when they fail, they fail, and are not intermittent. The saga continues and I'll keep you informed. Thanks again.

 

PS to that last post. Still haven't found the color coding for that AMM plug on line. It's the 6 terminal plug with only 1-5 being used but all the ones I find on line are just 4 pin?

 

there's two main versions of the AMM/MAF used on these cars, LH 2.2 cars up to 1988 (and 1989 turbos) used the "007" MAF, while LH 2.4 cars from 89+ (turbo 90+) use the 016 MAF.

on the diagrams for my 1992 turbo, the wires are ...

1 - brown - ground
2 - blue-green - to pin 6 of the ECU (signal ground)
3 - blue-red - to pin 7 of the ECU (signal)
4 - blue-white - from pin 8 of the ECU (burnoff control)
5 - blue-yellow - power from the main FI relay.

pin 6 is only used on euro B230GT models.

wire colors have been known to vary by year/model.

 

Yesterday we drove 330 miles from St Louis to Nashville with no problem. Headed to Knoxville on I-40 today and have found our selves on the shoulder twice. Tried to jumper the relay but that didn't do any good. Then replaced the presure-regulator which was just a shot in the dark but that only got us 30 miles. We've sat for the required 15 minutes and are about to start again, we hope. Engine temperature is perfect by the guage but I'm sensing a corellation with temperature under the hood as in after running at highway speed for a while and then entering slow construction speed has been followed by a flame out twice. Getting desperate for that silver bullet!!

 

It’s been about 10 days since my last forum post about the spontaneous shut downs of my 93 Volvo 940T and I wish I could say that the issue has been resolved, but … it aint! I have replaced numerous parts along the 3,700 miles since we started experiencing these incidents which total 18 as of today. I now strongly suspect that it is a heat related wiring issue under the hood as it has occurred with greater frequency in the hot humid weather of Tennessee & North Carolina. As of now we are always able to restart when adequate cooling takes place. Engine temperature has never been up and there is no coolant use, radiator and all hoses are new. Although I try desperately not to drive at night, it has never occurred in the cool of the day or evening. We are now in that ugly megalopolis stretching from DC to NY so this is potentially a serious safety issue.

This is the most difficult type scenario to diagnose as it can’t be predicted, or caused, and the engine won’t run long enough to get the hood up and wiggle connections or wires. The only code that shows up occasionally is 1-2-1 which suggests a wiring problem to the Air Mass Meter but again, that could be anywhere. A post I read said that a similar scenario was remedied by replacing the Fuel Pump Relay. So I did that but to no benefit. I even did the old coil replacement which dishonest shops always pull on uninformed customers, but again to no benefit, so I now have a back up FP Relay & Coil.

When/if we get to NJ I’ll likely spring for a rebuilt AMM but I’d sure like to have some ingenious diagnostic tips to learn if this is in fact what is causing the problem. It’s a lot of money to spend on a hunch. TD

 

In searching for possible heat related wiring issues there is a black box, about 4" square covering something on the firewall right by the distributor. It's bolted to the firewall with one bolt at the top (engine ground straps connected to top bolt) and two bolts at the bottom. There are no wires or plugs connected to it. What in the world is it? I can't find an image on line anywhere. TD

 

So I finally found it. It's called an Oscillation Damper? So what the heck is that? Could it be causing my engine to just shut down?

 

oscillation dampers are typically just dead weights, sometimes rubber mounted, positioned strategically to dampen out inherent oscillations/vibrations. you should see the 20+ lb lead counterweight mounted on the left front strut tower of my Mercedes 300CE Cabriolet, hah.



Mercedes calls this a vibration absorber.

 

That lead weight seems like it might dampen some oscillations, but what's inside that box on the 940 and why on the firewall? I can get it being on the strut tower, but ....

 

maytbe the firewall was prone to vibrating at a specific characteristic frequency. bolting a weight on it is a way of changing that frequency to one thats either less annoying or won't happen.

 

Just want to wrap up this thread which began 34 posts ago on July 23 in Pocatello Idaho. Our journey to my 50th high school reunion in the "Demon possessed 940" has ended after 7,800 miles from Oregon to NJ and back. We found ourselves stalled on the side of various Interstates, US highways, state highways, etc, a total of 28 times. Each time we were able to restart after 15 mins and travel on for as much as 200 miles or as little as 4 miles, once we had cooled off the engine compartment to varying degrees. (no pun intended)

Although I don't yet know what is causing this, (and probably won't till next summer) I know it has to do with the ambient temperature under the hood, not the engine temperature which has never risen above normal, nor thrown any logical codes. I DO know that the problem is NOT ...

-either fuel pump or filter
-crank position sensor
-Fuel Pressure Regulator
-Ignition Coil
-Fuel Pump Relay
-Ignition Control Module
-loss of supply voltage to
Coil, injectors, AMM

If I ever find the problem, I'll post it here, but it probably won't be till next summer!! TD