Any ideas on this anyone ?
- Thread starter peanut
- Start date
Have you got access to a fuel pressure gauge? There's a point on the end of the fuel rail to attach it to so you can check the pressure. If the damper or regulator fails I don't know what happens to the fuel pressure but it might just pump around the delivery and back down the return line. Not sure how it would ever run in that case though I guess.
peanut
Active member
the TPS being out of adjustment wouldn't stop the engine from firing. If the AFM were faulty you wouldn't get a perfect running engine when warmed up. This has to be something that creates a fault when cold but rectifies when warm and then gives no further problems if the car is used frequently The problem returns when the car is left unused for a couple of weeks
Faulty AFM and TPS wouldn't cause this sort of intermitant fault it would surely be present all the time wouldn't it ?
peanut
Active member
I don't but I should be able to get hold of one .
If the pressure damper and regulator were faulty I would expect them to be faulty during running but there are no symptoms when running and none even when cold the next time ?
This intermittant operation rectified by frequent use seems to suggest some sort of poor connection problem associated with or causing incorrect fuel delivery when cold Agrrrrrrrrrrrrrr
rcsalmons
New member
I think you are measuring a permanent 12v signal to the injectors.
You will be looking for a pulse which cannot be measured by a meter, you will need an oscilloscope. The pulse will be grounding the other side of the connector - the length of this pulse will vary depending on how long the injectors need to fired for.
Rich
You will be looking for a pulse which cannot be measured by a meter, you will need an oscilloscope. The pulse will be grounding the other side of the connector - the length of this pulse will vary depending on how long the injectors need to fired for.
Rich
George Elliott
New member
Peanut,
I'm guessing, but a couple of ideas:
I agree its fuel thats the problem.....
I'm confused by that stuff that looks like grease in the connectors.......as suggested get rid of it.
The fact that the car will run once its eventually started is good, there can be nothing wrong if it runs like that - but there is.
The time delay is the thing that reintroduces the problem - agreed?
If so whats happening - is the fuel running back to the tank (the non-return valve which is built into the Fuel Pump should prevent this)
Is the Valve stuck perhaps, is the Fuel line airlocked, and the throttle operation while cranking is slowly bleeding the air out of the rail?
Is the Tank vent OK, take off the fuel cap and check if the problem changes behaviour.
I know a guy who had a similar problem, he removed the rail & injectors, reassembled the lot in a clear Poly Bag and cranked the engine. You can watch the injector spray operating allegedly [8|].
Also, is the Fuel Rail Damper, and Pressure Reg OK, - they must be for it to run I guess?
Has any work been done to the car - anything pre this fault?
Good luck
George
944T
964
I'm guessing, but a couple of ideas:
I agree its fuel thats the problem.....
I'm confused by that stuff that looks like grease in the connectors.......as suggested get rid of it.
The fact that the car will run once its eventually started is good, there can be nothing wrong if it runs like that - but there is.
The time delay is the thing that reintroduces the problem - agreed?
If so whats happening - is the fuel running back to the tank (the non-return valve which is built into the Fuel Pump should prevent this)
Is the Valve stuck perhaps, is the Fuel line airlocked, and the throttle operation while cranking is slowly bleeding the air out of the rail?
Is the Tank vent OK, take off the fuel cap and check if the problem changes behaviour.
I know a guy who had a similar problem, he removed the rail & injectors, reassembled the lot in a clear Poly Bag and cranked the engine. You can watch the injector spray operating allegedly [8|].
Also, is the Fuel Rail Damper, and Pressure Reg OK, - they must be for it to run I guess?
Has any work been done to the car - anything pre this fault?
Good luck
George
944T
964
peanut
Active member
good post George thanks for the input
I think you may be closer to the truth than either of us realise.
I've just been re-aquainting myself with Clarkes Garage and I read this about the fuel pressure valve
One of the most common failure modes for the FPR is to fail closed to the point that fuel rail pressure is extremely high. The high differential pressure across the injectors causes them to draw excessive current. The excessive current is seen by the injector drivers which subsequently shutdown. If you have a condition where the car will not start or starts and almost immediately dies, try disconnecting the wire for one (1) injector. Attempt to start the engine. If it starts and continues to run, the fuel pressure regulator is likely bad. Bear in mind that running on only three cylinders, the car will run very rough. By disconnecting one injector, it reduces the current enough to keep the injector drivers from shutting down.
Now this would also explain the melted plastic in the injectors connectors I originally posted about . Excessive current drawn due to over pressure of the fuel system due to a faulty Fuel Pressure Valve which also shutting down the fuel delivery to the injectors .
Tomorrow I am going to disconnect one injector and try start . If it starts I'll have my culpret.
I think you may be closer to the truth than either of us realise.
I've just been re-aquainting myself with Clarkes Garage and I read this about the fuel pressure valve
One of the most common failure modes for the FPR is to fail closed to the point that fuel rail pressure is extremely high. The high differential pressure across the injectors causes them to draw excessive current. The excessive current is seen by the injector drivers which subsequently shutdown. If you have a condition where the car will not start or starts and almost immediately dies, try disconnecting the wire for one (1) injector. Attempt to start the engine. If it starts and continues to run, the fuel pressure regulator is likely bad. Bear in mind that running on only three cylinders, the car will run very rough. By disconnecting one injector, it reduces the current enough to keep the injector drivers from shutting down.
Now this would also explain the melted plastic in the injectors connectors I originally posted about . Excessive current drawn due to over pressure of the fuel system due to a faulty Fuel Pressure Valve which also shutting down the fuel delivery to the injectors .
Tomorrow I am going to disconnect one injector and try start . If it starts I'll have my culpret.
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