Bjbpe

If I give the engine a small shot of either it will fire but will not continue for more than a couple of seconds. I suspect the fuel filter and will install a new one tomorrow. If that does not do the trick, I'd appreciate any suggestions from those who have more experience and less age than I have.

RPetty2

Fuel pump
If not that, Check the fuel regulators

Schocki

Remove the multipin plug from the LH-ECU to prevent possible damage to the brain. Pull the fuel pump relay and insert a bridge. You should hear the fuel pump running. If not there is your fault.

If the pump runs, remove the bridge and connect the plug to the LH-ECU again. Swap the fuel pump relay with the horn relay. They are the same and many times the fault lies in a broken fuel pump relay.

Fuel pressure regulators: pull the vacuum connectors, if you smell gas the internal diaphragma is broken.

Let us know what you find...

Dave928S

Barney ... first off try the two most simple solutions which may be preventing your fuel pump running ... the fuel pump fuse and relay. It would seem likely to be a fuel pump issue if it runs for a short burst with ether.

The fuse will be simple to check visually and the relay can be temporarily swapped with a known good one.

The fuel pump fuse is #42 and is 15 amp .... if it's failed and you haven't got a spare take the one from #18 which is for the horn and is the same amperage.

The fuel pump relay is number XX ... and can be swapped to check using relay number XII which is for the horn.

If the horn works you know that both the fuse and relay are OK to try in the fuel pump positions.

If that doesn't do the trick then it may be a failed fuel pump. If you bridge the relay terminals to supply power to the fuel pump continuously and it still doesn't run ( you should hear it) .. then check the fuel pump terminals with a multimeter .. if power is at the terminals and you still don't have a running pump then it's failed and needs replacement.

Hopefully it's just a fuse or relay and you don't have to keep looking.

Edit: .. and what Shocki posted while I was

John Speake

Be very careful to identify the correct pins when jumping the fuel pump relay. It can blow up the FP driver in the LH ECU if you get it wrong.....

Schocki

Hi John,

that is exactly why I told him to remove the multipin plug on the LH-ECU BEFORE inserting a bridge into the relay base.

"No brain, no pain "

John Speake

Hi Schocki
Yes I saw that you recommend that, I was reinforcing what happens if he ignored you :-)

Bjbpe

To John and Shocki:

Thanks for your recommendations and, especially, your reinforcing. Given my level of ignorance, the warning is particularly important.

I haven't had time to do anything yet but the fuel pump only has about a thousand miles on it. I accept that all things are possible, especially for a guy who hates chasing electrons; however, should the fuel pump be OK, does anyone want to suggest where further to look.

All comments are appreciated.

Schocki

If the pump is ok. It can only be the fuse, relay or bad wiring.

I don't think the LH-ECU is bad, because it runs with starter fluid.

John Speake

You have established there's a spark and that's an important first rquirement. With an output from the EZK ignition ECU to pin 1 LH ECU then the LH won't start the fuel pump or open the injectors.

Follow Schocki's suggestion and disconnect the LH ECU and bridge the FP relay. If it make a noise that's a good sign, but does not always mean that it is pumping fuel sucessfully to the injectors at the right pressure. To check fuel pressure and flow means breaking into the fuel system.

First, let us know how you get on with the FP test.

Bjbpe

The very dim light bulb in my brain just came on. I'll check the fuse first. Thanks men!

Dave928S

And if the fuse is OK the next simplest thing is to swap the relay with a known good one (horn) as per my post #4. Make sure you have a good fuse and relay before doing anything more involved ... often it's the simplest thing.

dr bob

Since you worked on the fuel pump recently, it's worth a look to see if it's something easy, like the wire came off the pump. And, why was the pump replaced?

Power for the pump is delivered through a dedicated feed from the battery. One of those smaller red wires connecetd to the positive battery terminal (the other two are for the radiator cooling fans). Clean all of them (and the battery terminals...) to bright-and-shiney, snug them up. Been in the battery well recently?


My car stranded me at the bottom of the driveway when the fuel pump relay gave up. Pump still ran, but not enough current to make adequate fuel pressure. Diagnosed with a fuel pressure gauge and a jumper after I dragged the car back to the garage. New relay was in the boot. Should have tried that before dragging the car back up the hill. Missed lunch with Rob and Greg B that day.

Bjbpe

Thanks to all with good ideas. As a 78+ oldster I take on the important things first. Important #1 is to get another day of skiing in at our local mountain. Important #2 is to get at the pump Important #3 was going to work today to earn the money to use on the car. Saturday, I devote the day to getting to the bottom of the problem known as important #2.

Stromius

Bjbpe...check your TempII on the waterbridge too. Simple ground to post check with your multimeter will tell you if your sensor is malfunctioned. See pg 8 below.

Great document that's reference for engine systems from Eletronik Repair:

http://www.porsche928forums.com/down...ineControl.pdf