Hi y'all. I found this place looking for help on Google. Odds are there is someone on the planet who has experienced this and can help. I have an 85 240 Wagon, B23F I think, and according to my Haynes/Chilton it has the 84 Bosch Jetronic II setup, as opposed to the 85, based upon the fuel relay setup, with two little cubes.

I'm new to Volvos. What I have is the main fuel pump relay operating intermittently at switch on, or even failing after extended run time (apparently, which has stalled my daughter on the road, but she gets it restarted after several tries. I can operate the ignition switch say 6 times, and two of those the pump will come on and stay on, and the car will run as long as I leave it running. The ignition switch is fine, (I have had it apart to inspect and test the contacts), and sends battery to the ECU in position 2, which the ECU sends to the problem relay on a red-blue hot wire which operates the relay contacts and sends the constant hot (reds)through the relay to red/yellow to fuel pump fuse 5 in the panel to the pump.

On the downstream side of the blue red from the ECU which operates the relay at full battery voltage is a green/blue-gray which goes back to the ECU. When the relay operates properly and turns the pumps on, the green/blue back to the ECU reads maybe 2.7V, consistent with proper drop across that relay contact actuation coil back to whatever ground or low-voltage circuit in the ECU provides that necessary voltage differential. When the relay does not operate and turn on the pumps, that green/blue return to the ECU is a full battery voltage.

Does anyone know of a signal condition from any component of that car which can tell the ECU to shut off that relay???????????!

I have of course cleaned every ground on the intake manifold and firewall, ohming them back to neg at the battery to be sure. I have read the plug on the ECU disconnected to ohm ground pins, temperature sensor, air mass meter, throttle switch, etc., taking great pains to figure out the pin numbers which were not embossed. There was one ground pin which was maybe 4 ohms, but I believe I have that at .3 or so now, in case that was critical. The temperature sensor read 4900 ohms, but it was around 20F degrees with wind chill, and unpluging the sensor makes no difference in this relay condition.
In short, I have tried to eliminate peripherals and find nothing bad.

The fuse panel is fine with brass fuses, I have removed and tightened the connectors to this fuse. I have dropped the main pump shield and unplugged the pump, and the difference in draw makes no difference in this intermittent relay failure. In other words, I do not think I have a pump problem. If the pump were heating up enough to short the relay, it should not only blow the in-line fuse, but heat the relay. (Yes, the in-tank runs fine when they work - I stuck a funnel in there and listened) I have of course coughed up for some Beck-Arnley relays (cross referenced - $10 each instead of $60 for the Bosch), and it makes no difference, because that full battery voltage on the green blue side from the ECU precludes the relay operating.

Today, I drove 3 hours to a Volvo junkyard in the big city to get an ECU cheap,(thinking I had eliminated all other possibilities), ($100), and installed it only to have a worse problem. With the replacement ECU the battery voltage is there on the green/blue constant, so the relay NEVER operates. It is an aftermarket unit, and supposedly tested good. What is interesting is the Bosch unit which was in there sometimes operates the relay, but this one never does, once again indicating either something is signalling the ECU to shut down the pump, (which everyone I talk to seems to swear there is no such animal), or else this ECU has the same problem as the other one only worse (what are the odds of that).

Sorry to be so long-winded, but the next step is I will jumper around that relay (isolating those two wires from the ECU which operate it), and let the engine run for an hour or so to be absolute on the pump integrity, but I lay pretty good odds that's not it.

Ok, that's about it, unless you want to hear how this Volvo almost turned into a bomb on my daughter before from the fuel regulator diaphram failing and pumping the engine full of gas on cold start, (I didn't find it until I had #1 open checking for spark and shot gas ten feet - it literally started leaking out the rear mainseal), or how the stator/sensor magnet in the distributor failed. In case it matters for this problem, I cleaned, ohmed, and put rings and caps on the injectors after that to make sure none of them stick open. This is a 165K car, friends, and the machine is tight, but it has been the Volvo from hell. All I wanted was good cheap safe reliable transpo for the girl. Do they like have a hidden factory camera installed in some of these with an up-link so they can sit and laugh at the guys that get them?

Thanks for any help. BTW, I popped open the old ECU, but there is no possible way to troubleshoot that thing without a factory test jig, values, a schematic, and a scope. Zener diodes and switching transistors I can handle with a VOM, but that things is full of ICs.

Alley Oop