fuel pump relay again.

[Offgrid]

Some time ago I had to replace the fuel filter relay on the B230E engine. The car wouldn't start, and the fuel pump was running with the ignition off, and not running with the ignition on. This would seem to be less than optimum functionality, and I replaced the relay. After much discussion and research, I bought a new green mechanical relay, and the engine has been running well after this replacement.

Yesterday I visited Hayling Island, which was a big mistake. There was a water main being replaced on the only road that can be used to leave the island. It took me over two hours to tavel a couple of miles in the Estate ( B200E engine ).. It was one of those jams where you move forward a couple of car lengths, and then wait for a few minutes before moving another couple of car lengths. I've got a battery problem and a sensor problem, so the engine was idling at about 1,500 revs, and I didn't want to turn it off. The engine stayed at normal temperature throughout. Just before the traffic lights at the roadworks, the engine died on me, and it refused to start.

I noticed that the fuel pump was working when I turned on the ignition, and when I felt the relay, it was red hot. At that point I gave up and went home. I returned today with the relay from the B230E, and on fitting it the engine fired up after it had pushed a bit of fuel up to the engine. So now I have 2 dead relays and one working one - all are green mechanical ones. I've been online to buy a replacement, and now all the information I find states that redblocks after 1885 need to use the white electronic relay, and I've ordered one of those to see if it is better. The current green one is slightly warm after having driven home and to the suoermarket, but is working well.

So what is the truth? I'd rather use the white one. Not only because it is £11 rather than £17 for the green one, but because the green ones don't seem to be available at a reasonable price. What difference does it make if I use an electronic one? I gather the relay is dual function, but I'm not sure what the second function is.

[classicswede]

Green relay for K jetronic engines (B21E B23E B200E and B230E)

White relay is for LH injection so B23F B200F B230F (inc FT, FK and GT engines)

The white relay is available in both original and aftermarket

The green relay is now not available original. The aftermarket ones are not great. Best to have one fitted and one as a spare in the glovebox

https://www.classicswede.org/shop/gr...mp-relay-k-jet

[Ian Fife]

I gather the relay is dual function, but I'm not sure what the second function is.

I may be mistaken here, but I think these relays are in fact two relays - one which works when cranking and then switching to the second when the engine fires.

I was told this when I had a fault with my 945, it would fire and run very briefly and then cut out. So a fault with the second relay was diagnosed. Changing the (white) relay effected an instant and permanent cure.

Ian F

[classicswede]

Originally Posted by Ian Fife

I gather the relay is dual function, but I'm not sure what the second function is.

It operates as a relay for the fuel pump. The second function is a safety car relay. Should the rpm signal to the relay stop the relay cuts the fuel pump, that is the reason of the rpm signal wire going to the fuel pump relay

[Offgrid]

Classic Swede is in agreement with the information that I discovered when I replaced the relay on the B230E, but it doesn't seem to agree with the information I have discovered recently. I've also tried to discover what will happen if I use a white relay on a 1990 B200E - that is the one Ebay seems to think I should be using.
I'm also concerned by the small amount of heat I detect on the relay, and I wonder if that is the result of a faulty sensor. causing the relay to oscillate or something. That would explain the failure in heavy traffic.
I'm also considering the implications of the secondary shut off relay. When I switch on the ignition, I can hear the fuel pump for a second or so, and then it turns off. If I turn off the ignition and turn it on again, then the pump will run again for another second or so. This would seem to be a good way of priming the fuel line rather than possibly draining the battery by cranking the engine.
I think I'm going to cut the top off one of the broken relays, and see if I can repair it. I could then keep the repaired unit for emergencies.

[Ian Fife]

I got my information from a Volvo trained mechanic who now runs his own Volvo business,

Ian F

[Offgrid]

Originally Posted by Ian Fife

I got my information from a Volvo trained mechanic who now runs his own Volvo business,

Ian F

You were lucky to find someone who knows about car components. Most so-called mechanics these days seem to be either software engineers, or fitters.

I've taken the covers off the two failed relays, and they are very different ( although they are both green ). The one that failed in the traffic jam has got a wire that has become de-soldered, and the insulation has melted slightly at the end. This ties in with the fact that the case became red hot. I'll resolder it, and see if it works, if so, I'll keep it as a spare. I'll have a look at the wiring diagram, and see if I can work out where the heat came from. Since fitting the replacement, the car seems to be a bit friskier, and the starter disconnection hasn't returned. I'll give it another couple of days before forming a conclusion about that issue.

The reversed functionality of the earlier failed relay will require a bit more research. I'll keep you guys posted when I get round to doing that.

The white relay has arrived, and it appears to be identical externally. The connectors and lugs are all in the same locations. I haven't had the courage to try it yet. I might do that on the saloon, but it doesn't have a back box right now, and the neighbours complain if I start it too often.

[Offgrid]

OK
Here is the definitive answer for a 1990 B200E engine.

Green ( mechanical ) is the correct relay. With it fitted, the pump runs for a couple of seconds on turning the ignition key, and the engine starts.

White ( electronic ) doesn't work. The fuel pump run continuously when the ignition key is turned, and the engine doesn't start.

Apologies to anyone who's opinion I called into question.

[classicswede]

Told you so

The relays do get hot as they are a high load relay and that is why the soldering can let go. As the soldering starts to fail the relay gets hotter

The covers unclip easy enough to look at them. You can sometimes repair them

Stop looking for information in the US as it does not apply to UK cars

[Rversteeg]

The 2 seconds priming function is not in the relay itself, but in the ECU.
The name fuel pump relay is a bit misleading as it is actually a dual relay with a primary one powering the ignition and injection system and a secundary relay powering the fuel pump(s). Quite a crucial relay in the heart of ignition and fual system.