'90 405 SRi - fuel pump running continuously & not start

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paradox
Posts: 9
Joined: 23 Jan 2005, 12:43
Location: New Zealand
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'90 405 SRi - fuel pump running continuously & not start

Post by paradox »

Hi, having some trouble with my '90 405 SRi, XU9J2 with L3.1 Jetronic.

It's very intermittant, for example it will decide to stall in traffic, if you get it restarted it will run very on/off like. So if you accelerate one second it will pull nicely then completely cut out the next, basically cutting in and out very jerkily. If you sit in neutral and try hold the revs at 3000rpm it will drop down then come back up again a cycle. Drive it for a few minutes it will come right and drive fine. It's worth noting that when you do put your foot flat to the floor it pulls fine, it's when you drive it partial throttle that it cuts in and out.

When it is playing up, chances are if you stop it won't start, and I have observed that when it won't start or is playing up like this, the fuel pump is running continously with ignition on, not stopping after a couple of seconds like it should.

I guess my question is, what can cause the fuel pump to run continously? I'm very confident that there is a connection between these problems and the fuel pump running continously. This has been happening occasionally for a year and whenever it won't start or does manage to start but cuts in/out I can be certain the fuel pump is doing the continous running pattern.

A bit of background, about a year ago when I bought the car it started doing this, the mechanic found an aftermarket relay that was running the fuel pump continously, once this was removed the car started up and ran fine. It has however occasionally played up in the manner I've described over the last year though.

Someone told me they encountered a similar problem on a 205 GTi (I know different car but still, an XU9 motor with L-Jetronic) with the fuel pump running continously with the ignition on. They said they swapped the "large 7 pin relay which is located next to the ECU on late 205's, behind the headlamp on newer ones" and it stopped doing it.

Am I correct in thinking that the fuel pump relay is the tachymetric relay? Where is this located in the 405? I'm aware of the fuse box close to the drivers side strut, and the black box mounted on the side of the engine bay but located quite far back by the passenger side of the firewall. In this box on the passenger side by the firewall there are essentially three connectors, two have little black boxes connected which I presume are relays, one has nothing connected to it.

Any advice would be appreciated, this has been driving me nuts.
paradox
Posts: 9
Joined: 23 Jan 2005, 12:43
Location: New Zealand
My Cars:

Post by paradox »

Anyone?

I'm just keen to locate the relay, there's the black box in the back passenger side corner of the engine bay with two relays, but I'm not sure which one is the tachymetric.
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