Fuel solenoid shuts off after a few seconds - ECU security is disabled.

[JackG]

2003 Jetta ALH. I have 2 security-disabled ECUs. Both worked fine prior to this. Swapped them. Not the problem. Recently replaced fuel injector nozzles in kind (0.205mm).
Crush washers did not come with the rebuilds. Tried using the old washers. The nozzles leaked (no surprise) but the fuel solenoid shut-off valve (on the injection pump} shut off after a second or two (confirmed with a volt meter). Behavior one would expect with a security-enabled ECU as power to the valve comes directly from the ECU. Any Thoughts? Help!

 

[oilhammer]

What are you trying to solve?

Complaint

Cause

Correction


Give us the first C.

 

[KLXD]

That's normal for any IP. When you start cranking the motor the voltage should come back.

So answer the the previous question.

 

[JackG]

The engine won't start. the shut off valve closes before the engine starts.

 

[turbodieseldyke]

Try hot wiring the solenoid and see if it will start.

 

[JDSwan87]

Wait a second... you swapped nozzles, did you bleed the injectors? (Wondering if you have air in your lines).

 

[Vince Waldon]

It's a little tricky to know exactly who is the chicken and who is the egg, since the ECU will shut off the solenoid if the engine cranks for a while but won't start.

Temporarily disconnecting the solenoid and hot-wiring it directly to a constant 12V might be one way to narrow things down.

 

[JackG]

Air in the fuel was a problem which I think has been fixed. All new fuel lines from the hard plastic lines at the firewall to the filter and pump. New filter thermo T. We installed a reciprocating solenoid pump in line to feed the IP. Excellent flow now when bleeding the injectors. It's the damn shut-off solenoid that shuts after a few seconds. I'll try hot-wiring the shut-off valve. Good idea for the next step. In trying to rectify this problem we have installed a rebuilt IP, timing belt change (it was due), crank sensor, N75, MAF. I'll be getting back to the problem in a week or so and I'll report the results. Thanks for your thoughts.

 

[jimbote]

If the only thing you changed was the nozzles then you have air on the system or something is really screwed up with the nozzle install. Solenoid clicking off after a few seconds key on is 100% normal. It's a safety feature that prevents fueling if no crank rotation is detected.
It can be difficult to bleed the pumps on these. I always pull from the tank and push through the filter with 100% success rate and very fast bleeding. If you're sucking through the pump return, that's the slow, miserable way to get the air out. Use a boat primer bulb between the tank and filter. Loosen return banjo nut and return fitting. Pump bulb until bubble free fuel runs out, tighten those two up and bleed lines @ injectors.

 

[JackG]

jimbote, "...is 100% normal. It's a safety feature..." I think this is the answer that I was looking for. An ECU generated response similar to the security feature (which has been neutralized.) When I get back to working on the car in the next week, I'll have direction. I'll post the results. Thank you!