Fuel pressure regulator fault?

[whiskychaser]

My car starts first time, every time. Well until this morning. Turned the key, it ran for a few seconds and died. Wouldnt restart so I didnt want to flatten the battery trying and got a lift to work. I'm thinking fuel problem so tonight with a torch and +1 temp I check the fuel pump fuse and thats ok. So i jumper the fuel pump relay. I can hear the pump humming nicely under the boot carpet. But I can also hear fuel coursing through the pipes under the bonnet. Try to start it and get a cough. Encouraged I give it a few more goes and she will try to run but dies. I think I can smell fuel so I pull the jumper and replace the relay. Eventually she starts and idles normally. So two questions:
1. Should I have heard fuel rushing round the pipes? I'm thinking it should reach pressure and then stop until the injectors release some pressure
2. If I SHOULD hear it flowing, what did I do to to make her start?
I've already ordered a fuel pressure gauge but as that wont be here by 6.30am (when I need the car again for work) I'd appreciate any advice pdq

[Blitzkrieg Bob]

Yeah, there should be some fuel return.

The fuel system is a loop, pressurized up to the injectors and released to a return line via the regulator.

[Sailor]

No you should not really hear the hiss of rushing fuel. If you replace the pump with a new one the flow is quit. Time for a pressure check to let you know for sure. It is simple just 'T' into the the system before the pressure reg. I do it in the trunk @ the top of tank. Then I check the return for pressure should be no pressure in the return. The fuel bowl in the tank can clog at the exit of the return, causing very high pressure.
Black tall pipes and poor gas mileage indicate high fuel pressure.
The first thing I would do though is unplug the MAF and see if the car runs better. You will throw a code but most times the 92 MAF fails it does not throw a code. If the car runs normal then it is the Maf. If you still hear the hiss you may want to start looking for a fuel pump. The hiss usually means that there is not much flow thru the reg.

[whiskychaser]

No you should not really hear the hiss of rushing fuel. If you replace the pump with a new one the flow is quit. Time for a pressure check to let you know for sure. It is simple just 'T' into the the system before the pressure reg. I do it in the trunk @ the top of tank. Then I check the return for pressure should be no pressure in the return. The fuel bowl in the tank can clog at the exit of the return, causing very high pressure.
Black tall pipes and poor gas mileage indicate high fuel pressure.
The first thing I would do though is unplug the MAF and see if the car runs better. You will throw a code but most times the 92 MAF fails it does not throw a code. If the car runs normal then it is the Maf. If you still hear the hiss you may want to start looking for a fuel pump. The hiss usually means that there is not much flow thru the reg.
Thanks for the responses. I should make it clear I could only hear the rush of fuel when i jumpered the relay and the engine wasnt running. I have ordered a pressure gauge and that should arrive soon. My daily drive is only about 8 miles to work and back. The engine started fine this morning and tonight so at least I got to work and back. The OBC shows 14 mpg but that more than doubles if I a do a distance of say 60 miles, part on the motorway. Will warm up the lap top and see if any codes are stored. And report what fuel pressure I have when the gauge arrives. I can take a lot of stabs of what it MIGHT be but as the bugger now fires up as normal diagnosis is difficult. Apart from fuel pressure and stored codes, anyone care to add to the check list?

[Dave M]

The M50 should push ~50psi (M20-M30 ~43).

I've tested the fuel pressure on mine in order to locate a stumbling on acceleration. I have a solid 50 psi from the pump. When the pump relay is 'jumped', I also hear the fuel gurgling through the lines. Mine has only failed to start once, and we're talking two years of very, very periodic issues. Fuel filter and pressure regulator are next on the list, then I might consider fooling with the pump again.

I'll be watching this thread.

Dave M

[whiskychaser]

The M50 should push ~50psi (M20-M30 ~43).

I've tested the fuel pressure on mine in order to locate a stumbling on acceleration. I have a solid 50 psi from the pump. When the pump relay is 'jumped', I also hear the fuel gurgling through the lines. Mine has only failed to start once, and we're talking two years of very, very periodic issues. Fuel filter and pressure regulator are next on the list, then I might consider fooling with the pump again.

I'll be watching this thread.

Dave M
Thanks for the response. I'm going to go about this methodically and intend to check the following:
1. Fuel pressure with the relay jumpered - should be 51 psi +/-
(If it isnt, intend to pinch the return to see if it increases)
2. Fuel pressure after the letting the system stand for 20 mins
(should be same)
3. Fuel pressure with engine warm and idling-should be 51 psi +/- with vacuum hose disconnected from the regulator
4. As 3 but with the vacuum hose connected.
5. Vacuum at inlet manifold

I expect the fuel pressure to reduce by about 0.5psi for every inHG of vacuum when the engine is at idle. Have it in my head I should be looking at 18 inHG so by my reckoning the fuel pressure would drop to 42 psi. Can anyone correct me on this plse?

[whiskychaser]

Received it safe and sound. Ad and pack state its good for up to 300 psi. Until you take a look at the (white) upper scale on the gauge which shows a max of 10!! WTF? Supplier is 'checking it out'. Meanwhile a crap photo - cant seem to post them from a proper camera as files are too big:

[Dave M]

1 bar or 1 atmosphere = ~14.5 psi. Could you be reading a bar or atmosphere scale?

It would be one silly fuel pressure tester with a max of 10 psi.

Dave M

[whiskychaser]

1 bar or 1 atmosphere = ~14.5 psi. Could you be reading a bar or atmosphere scale?

It would be one silly fuel pressure tester with a max of 10 psi.

Dave M
Supplier got back to me this afternoon. To quote you, Dave 'Its one silly fuel pressure tester' -the max IS 10psi!!!. Sealey and Draper are doing the same gauge so anyone buying one beware. The good news is that the car is running. And I can test the inlet vacuum. So my next job is to find a tool that DOES what it says on the can:(

[icesoft]

Carburated engines typically run less than 10 psi fuel pressure, and that's probably the type of gauge you received. You need an gauge for 'Fuel Injected' vehicles. Either way, the packaging is still incorrect.

FWIW, I can't recall ever seeing a fuel pressure gauge that clears 300 psi, most stop around 100 psi.

[whiskychaser]

Carburated engines typically run less than 10 psi fuel pressure, and that's probably the type of gauge you received. You need an gauge for 'Fuel Injected' vehicles. Either way, the packaging is still incorrect.

FWIW, I can't recall ever seeing a fuel pressure gauge that clears 300 psi, most stop around 100 psi.
I think you are dead right - its for a carb system. The pack even says its good for commercial vehicles which is why I thought the 300psi possible. Just tested my inlet vacuum at idle (700 rpm) and it reads 18in HG. The pack says run it at 850 rpm and I get 19-20 at that but I think thats just cheating. Got a couple of sources for a 'proper' gauge and will post figures soon as I get it. Thanks for the comments

[whiskychaser]

Got a gauge - has glycerine in the face to stop the needle bouncing when you run the engine. Anyway here are the results on a cold engine:
1. Engine off and fuel pump jumpered: 52psi
2. Engine running at idle 45psi
3. Pinched vacuum hose to regulator: pressure increases
4. Turned off engine: pressure drops to about 42psi
5. After 5 mins, pressure has INCREASED to 50psi
6. After 20 mins pressure still rock steady at 50psi
The pressure increase after switching off had me scratching my head for a minute. Then I realised its the pressure regulator doing its job properly. The results look pretty good to me:)