jksymz75

Started the car (‘93 Coupe 6 spd 93k miles) to pull it out of the garage while working on motorcycle. Started without issue.

A few hours later, attempted to start to pull it back into garage. Turns over, tach bounces but will not start.

Some details:

Could not hear fuel pump when turn ignition to “on” position. Lately the fuel pump has been clicking a few times before I start it but it didn’t click this time.

Fuse for fuel pump OK.

I removed DME relay and used jumper to try and start fuel pump manually. Could not hear it turn on.

I have not replaced fuel fuel pump or fuel filter in my 5 years and 20k miles of ownership. I have no record of PO replacing.

I do have evidence of rodents in the car. Even some droppings in the actual fuse box (how the F$&% did they get in there???).

When checking for fault codes, car tells me to check the Hall Sensor.

I’ll have some time to look at it tomorrow. I’m going to open fuel rail to see if there is indeed fuel coming to the engine. If it is, I will check ignition.

Could a faulty Hall Sensor cause a no start? Anything else I’m missing?

oz968

You don't need to pull the fuel rail ...put some aerostart through the intake and if it fires and runs its fuel and if it doesn't then its electrical .
If its fuel (it starts with ether) put your jumper wire back on and see if you have power at the pump if you have power there, then its a pump.
If its electrical start with your Hall Sensor

Peter

Yogii

Yes, my novice opinion is that a faulty Hall sensor could prevent your car from starting.
They are not that expensive, but access can be a bear. I understand that they fail just as often from heat expose than from real wear.
Just what I have heard...

-Yogii
AKA 968 Novice

thomasmryan

the hall sensor harness plug can become brittle due to the proximity to the header. check both sides of the plug. there should be a little clip made of spring steel that holds the plug in the bracket. ball head allens makes r&r of the hall sensor a bit easier.

I use dryer sheets on the boats/cars to deter mice. they usually venture up the cowl drains at the rear of the front fenders. they get a verbal warning, conditioned with some crumbs, then bread crust twist tied to the trap. 100% kill rate.chinamart has Wooster traps that are made in the USA.

jksymz75

Peter, this is great advice. I put an ether based quick starter in the air intake and it fired up, ran (roughly) for a few seconds and died.

Next I pulled the cover to the fuel pump open. I thought it’d be a good idea to try to jump the fuel pump once more so i pulled the DME relay and jumped 30 to 87b and the fuel pump did indeed kick on.

I tried starting the car with the fuel pump constantly running and it didn’t start. I then replaced the DME relay and tried again and it started for a couple of seconds, prob because there was fuel in the system.

Does that that mean my DME relay is bad? I noted tach bounce but the needle barely moves. Not sure if that counts as “bounce”.

Also, here’s a picture of my Hall Sensor, which doesn’t show any signs of deteriorating, externally at least.

shinrai

Sounds like a bad fuel pressure regulator.

jksymz75

Now that I think of it - there were times that the car wouldn’t start right away and I’d have to turn it over a few times and maybe give it a little gas or turn the key to off and then crank it again.

They were few and far apart enough that I didn’t really think it was a problem.

thomasmryan

did you clear the fault codes? if there is no hall signal, it doesn't know when to fire

whiff the vacuum line to the regulator. if it smells like fuel, odds are that it is bad. a fuel pressure regulator test requires the car to be running

oz968

The fact that it starts with a fuel source excludes the electrical side of the fault.
Its fuel related so could well be a regulator with a blown diaphragm.
I would pull the fuel hose off the inlet side of the rail and using a jumper wire check fuel pressure (do you have a test gauge) before it gets to the regulator to clarify your pump is indeed pumping . This will indicate pump/regulator. The regulator is controlled by spring pressure against a diaphragm which is overridden by vacuum when you lose vacuum the spring pushes the diaphragm raising FP. If the diaphragm is split you will lose fuel pressure. It hangs off the rail at the rear and returns excess fuel to the tank from the rail unless of course it is broken an returning all fuel to the tank with no pressure at all.
Peter

jksymz75

Thanks again, I’ll try this next time I can get in the garage. I don’t have a test gauge but can borrow or buy. Any recs for gauge are appreciated.

Do you think I can rule out DME?

Any chance its it’s just a clogged fuel filter? Clogged strainer (in the tank)? Or could it be the vacuum line going to regulator?

Limited time so want a checklist going back in.

oz968

I don't think its electrical due to the start with an alternative fuel source and the fact it starts and runs until it runs out of ether.
You need to check that you have fuel pressure at the inlet to the fuel rail and if so it can only be the FPR.
That's my thinking anyway.
Peter

jksymz75

Update - I tested fuel pressure at the rail. It’s there and within spec (58 psi) so that means fuel pump and filter are ok. Must be the fuel pressure regulator as suspected.

Ordering one one today and will post again once it’s installed.

FCP Euro is backordered. Pelican is $186 for Bosch (won’t even talk about OEM $$$). NAPA is $115 and then 20% off because I have AAA. Any opinions on where to order?

Jfrahm

How is the the FPR? Are the plugs wet when it won't start? Dripping fuel out the vacuum side?
Hall sensor won't cause a no-start, it'll reduce performance.

jksymz75

Not dripping fuel out of vacuum side. I did not check plugs but it’s a good idea.

Also, retailers have not had this part made by Bosch for about a year. Everyone is out of it so it’s either Genuine Porsche part, NAPA or dismantler.

jksymz75

Thinking about this, if I’m getting pressure at the rail, doesn’t that mean the FPR is working? I mean, isn’t that its job?

Leakdown test passed, too.