Hello All.
92 940 regina/rex mileage unknown but very high. sons car.
a pattern has developed as the car seems to stall after around 15 miles driving or if it does not stall when shut off the car will not re-start. pretty much happens all the time. seems like the car has to be up to operation temp for stall/no start. always starts when cooled down after a few hours.
before all this the fuel pump died and i replaced it with a Junkyard pump. the JY pump looked like very recent replacement and the sender it was attached to also looked almost new without even a hint of staining from gas.
what i have done.
tested the fuel pump with analog gauge T,ed in at rail and it reads 35psi. squeezed the fuel line and pressure went up past 60 psi real quick. think its good. it is a quiet pump compared to the scam tech pump that died = 2yrs?
the fuel pump relay gets very very hot and can only keep finger on the relay for about 7-10 seconds before OUCH!!! this seems suspicious?
tried a noid light on injector connector when would not start and it lights up.
JY parts i swapped i had on the shelf.
JY coil/power stage. cleaned coil contacts.
new fuel filter
new plug wires
new spark plugs
cleaned grounds on intake and right and left side engine bay.
known working RSR relay (from my car)
used/newer cap and rotor.
cps looks new and its 3 yrs old.
removed cat and confirm its not plugged. (this is always fun)
replaced fuel pump relay with 3 known good ones.
swapped out IAC valve with used one i had on shelf.
cleaned throttly body.
swapped out Fuel pressure regulator. used from shelf.
cleaned ground in trunk for fuel pump.
visually looked for vacume leaks.
i am out of ideas as i am no mechanic. any help will be greatly appreciated.
thanks
Mike

hello
still stalling. randomly
Hmmm. please buy this car! cheap.

hello all
its not pretty but hopefully it will help.
didnt make the wires long for a permanent install but for diagnosis.
soldered every connection.
will keep yall posted.

RPM sensor?

Heat associated failures often mean electrical parts are getting warm and failing.
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john

Hi John.
i have a few extras and it cant hurt to swap it out.
how bout that real hot fuel pressure relay? whatcha think about that?
thanks
Mike

Hi Mike,

If the hot relay (due to contact problems) is what is making the car stall (or not start when hot), maybe you could verify it by putting in a "naked" relay with the cover off.

If it then runs farther or longer before failing, that would might(?) point to the bad relay rack terminals like Art says, as the root cause.

Just a bump thought.


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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Hello Bruce
my attempt to start to make the relay ext.
all six pins on the bottom are now loose. any tips?


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Hi Mike,
Yes, I remember some or all of them were loose & shaky after removing coils etc. But I soldered wires onto them like that, and then packed J-B weld around them for support. I didn't have the right colors to match the original wiring, but was careful to connect "rack socket" terminal 30 to "extended socket" terminal 30, 86-2 to 86-2 and so on.

I'll bet Art had all the right wire colors, but they really don't matter as long as 30 connects to 30, 85 to 85, etc. Maybe 1/2 hour and you'll be done. Just double check each wire/terminal with meter continuity to be sure.

I think my wires were about 18" long, but am not sure now.


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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Hi Bruce.
the spare 240 harness i just cut apart has all different size wires going to the fuel pump relay connector.
86/1 is small diamater. 86/2 is small diamater. 85 is small diamater.
the other three seem to be fine.
can you tell me how important the correct size is when making the FPR extension?
im guessing/hopeing you may know without looking in a book.
Oh yea 1/2 hour? obviously you never seem me do electrical work.
thanks
Mike

The heavy current carriers are input 30 (powers everything in FI system), 87-2 (both pumps and O2 sensor heater, and 87-1 (ECU, AMM, IAC, Injectors, and RS relay).

The other 3 (85, 86-1, and 86-2) are just relay coils and coil grounds.
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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

Hi Bruce
so i made up relay extension like the pics.
i need to splice in the volt gauge.
looks like for the gauge i splice the + side into 87/2.
not sure where to splice the ground into. i guess i can run a wire to any
ground like the cigar lighter but i would rather splice into a ground at the
fuel pump relay.
from my LH 2.4 drawings of the fpr it looks like 86/2 would be the place to splice in the ground.
just dont really GET it when it comes to DC electrical stuff.
i have more experience with wiring a house but its different.
thanks for all the help
later
Mike

Yes, 87-2 is the pump power. Ground the meter minus to any place handy.

I wouldn't use 86-2 for meter ground because that's controlled by the ECU. If the ECU doesn't ground 86-2 for some reason (like no ignition), there won't be anything at 87-2, which could be confusing.

To keep it simple, you just want a good, solid ground to the car body.

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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

hi Bruce.
i put up a pic of my contraption at the top of this thread.
i did ground at 86/2 but i can change it to car body.
but might not 86/2 be good as because it would tell me if the ecu is having a problem and if the ecu is not having a problem it will still tell me voltage drop if wiring/connection is bad? thus serving two purposes?
or is my thinking FUBAR?
sorry for all the questions. its only easy if you know the answer.
thanks again
Mike

"might not 86/2 be good as because it would tell me if the ecu is having a problem..."

You will lose that ECU ground anyway if the engine stalls for any reason (no ignition pulses to ECU). Maybe it doesn't make any difference. But it confuses me to think about adding another variable to the mix.

I think Art's theory is to watch that pump voltage to see if it drops down over time. Maybe he will chime in and straighten us out on this.

P.S. Your "contraption" looks good but it might be hard to get an accurate handle on voltage level with that dash meter. I was thinking you'd use a regular Digital meter.



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Bruce Young, '93 940-NA (current), 240s (one V8), 140s, 122s, since '63.

hi Bruce
hooked up the DMM and ground to seat bolt.
drove over 40 miles with two short stops and couldnt get it to stall/not start.
DMM stayed steady at 13.2 volts on the output.
darn i failed to fail.
if im not careful i may accidentally fix the problem.
relay didnt get as hot as the other.
Hmmmm?
time will tell.
thanks again to all
Mike

Nice work Mike. In doing it, you've probably jiggled the loose or corroded (heat producing) junction enough to keep it from failing for a while. That you seemed to have changed things, makes it more likely you're in the right area.

Based on the memory of those charred 740 fuse blocks I've seen in the yards, I'd guess the problem is in the female connectors of the relay's socket. I'd be out on a limb here, but I would also guess a pro's solution, to avoid the bringbacks, would involve replacing the fuse/relay block, relay, and harness ends.

That would be kinda cool, though, if you saw the meter take a dive, then saw a corresponding dip in fuel pressure, all going back to normal when you wiggled the plug end of your extension cable.
--
Art Benstein near Baltimore

A closed mouth gathers no foot.

Hi Art
lets hope i accidently fixed it for now.
but time will tell.
thanks for the help.
Mike

hi Bruce.
o.k. i can/will easily run a ground to the body and remove the 52mm volt gauge and use my DMM. (should have known this)
hopefully i can get the car to stall and find the problem today.
I'll Be Back

Seems like this would be a tough one to pin down in a 940.

Though kinda subjective, excessive heat would have to generated at some loose, corroded, poor contact -- whether in the crimp of the relay socket female terminal as I suspect, or any of the remaining 7 metallic interfaces in the relay and relay socket.

An extender cable, like the one you and I both devised, to get the relay itself out of the ashtray, would be ideal for troubleshooting. My approach, if this continued to plague a car, would be to get a voltmeter (or even a test light) wired up tightly to the wire that feeds the fuel pump, so the voltage drop would be confirmed as the culprit. That would remove the doubt about whether the relay is normally warm or too hot because of that voltage drop.


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Art Benstein near Baltimore

Always remember that you're unique. Just like everyone else.

hello all
Bruce has told me about his relay extension. i tried to make one for testing overdrive relays for ebay sales and it looked real good but didnt work (DOH)
maybe i should try to make one up as you suggest it would be easy to tap into the relay with a volt gauge. looks like a 240 fuel pump relay connector which i have on the shelf. i also have the volt gauge and extra relays plus solder iron and wires.
So Art or Bruce would you have a pic of the inside of that relay so i could try to follow your lead and make one up?
also i was going to install my fuel gauge and leave it hooked up so i can look at the gauge when the car wont start/stalls.
looks like another fun weekend.
first real problem with the regina/rex car.
thanks to all for the suggestions.
Mike

Good morning Art,

Could you tell me please what you did inside the relay case that has the wires running through the cover?

Did you simply remove the "guts" of the relay and solder the wires onto the appropriate connections, making it a relay "extension cord"?

Randy

Did you simply remove the "guts" of the relay and solder the wires onto the appropriate connections, making it a relay "extension cord"?

Yes, that's it exactly. Junkyard parts.
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Art Benstein near Baltimore

Never test the depth of the water with both feet.

Mike, I'm with John and Steve on the fuel injection relay. They do generate heat normally in the coil, but not finger-burning heat. If the 940 is like any of the 740's I've seen in the yards, the fuse block cum relay panel is about to char because of poor contacts.
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Art Benstein near Baltimore

Don't be irreplaceable. If you can't be replaced, you can't be promoted.

Did you check fuel pressure when it has stalled and won't start?

I agree with Steve, that the relay shouldn't be that hot. Look at the relay base. Does it look like it has been hot? Like fuse 16 on the earlier 740s?
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john

It should not get that hot. Look for a fault in the connectors to the bottom of the relay (see the FAQ).
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See the 700/900 FAQ at the drop-down menu above right.