code 1261; no start, jumpy tach

[lole30]

fighting a problem with this car. 92 325i. Only starts when i spray carb cleaner in the intake, and stays on with throttle input. But runs very rough and CEL flashes. I pull code 1261 "fuel pump relay circuit" from the DME. While cranking the tach is jumpy goes up to 2k and all over the place.

Replaced fuel pump relay and CPS not any better. Checked pin 3 of dme to relay; looks good has continuity and .06 ohms. When I jump the the fuel pump directly to power it does not start either.

What kind of signal should I see come from the DME to the fuel pump relay?

Not sure really where to check next.

[jlevie]

If the problem were to be the fuel pump relay or the fuel pump control section of the DME, jumpering the relay socket would allow the car to start and run normally. Since that doesn't happen there is something else wrong.

A 1261 code can be caused by a wiring fault in the pump control signal, a bad pump relay, or wiring fault in the pump relay coil power. But it can also be caused by something that interfers with the timing data to the DME. Since you've replaced the CPS (I hope you used a new part), that isn't likely to be a suspect. That leaves the fusible link, engine harness or DME as possibilities.

[lole30]

yes brand new part from pelican.

where is the fusible link?

Is there anyway to test the dme is bad? what kind of signal should i be seeing coming out of the pin 3 on the dme?

[lennon]

fusible link is in the 2nd, smaller power wire running from your battery (to the DME). the fusible link itself is probably under the carpet on the passenger side/back seat area, just follow the wire. are you getting spark at all? i assume youre not getting fuel.

[jlevie]

yes brand new part from pelican.

where is the fusible link?

Is there anyway to test the dme is bad? what kind of signal should i be seeing coming out of the pin 3 on the dme?

At least you didn't compound the problem with a used part...

The only realistic field test for the DME is to swap in a known good unit. I'd do that before I replaced the engine harness.

[lole30]

fusible link is in the 2nd, smaller power wire running from your battery (to the DME). the fusible link itself is probably under the carpet on the passenger side/back seat area, just follow the wire. are you getting spark at all? i assume youre not getting fuel.

vehicle is getting both spark and fuel.

the vehicle can turn on if i spray carb cleaner into the intake, but runs very poorly after does not stay on without throttle input. CEL also flashes. I get code 1261.