<944> No Fuel to Rail?

neildeshpande · 04-22-2003, 08:52 PM

Gruppe:

I put in a new pump and new filter and 2 gallons of gas in a previously empty tank. The rail pressurized fine. I could open the cap at the top of it and pressurized fuel would leak out. I then removed the injectors for various reasons and depressurized the rail.

I shorted 30 and 87b on the DME relay socket and the pump runs (you can hear it), but no fuel comes to the rail. About 3 mins total of running the pump.

During the pump running, I have one injector out, the fuel supply to the regulator unhooked (should have direct fuel supply from the pump) and the return line unhooked. I can blow down the fuel supply line (I am assuming this is the line that goes into the fuel regulator like thing at the rear of the fuel rail) and hear bubbles in the tank so there is no obstruction.

I added an additional gallon of gas and had no better results. I don't think that is the problem.

Any ideas?

Neil Deshpande

neildeshpande · 04-22-2003, 09:24 PM

FRW:

How do I put air pressure in the tank? I don't have a compressor or a fitting to do that with. Also, should the pump not self-prime? What happens if you run out of fuel under 'normal' circumstances?

What about pouring fuel into the pump supply line from the engine side to prime it?

Neil Deshpande

Pike · 04-22-2003, 10:11 PM

What is a fuel rail? (this has been bugging me) Does my car have one?

neildeshpande · 04-22-2003, 10:14 PM

Quote:

Originally posted by Pike
What is a fuel rail? (this has been bugging me) Does my car have one?

It is the square cross-sectioned 'tube' that runs along the top of your cylinder head. It is supplied pressurized fuel by the pump. The pressure is regulated by the pressure regulator.

On the rail are mounted injectors, which are basically little electrically operated faucets, that open as required to let fuel into the intake manifold, from where the fuel is swept by inflowing air into the cylinders for ignition.

All gasoline cars should have a fuel rail.

Neil Deshpande

neildeshpande · 04-22-2003, 10:16 PM

Quote:

Originally posted by FR Wilk
Put some airpressure into the tank and run it again. The pump may be full of air and not doing anything.

FR Wilk

FRW:

It just occured to me that there may be non-return valves in the fuel supply line. So, if I ran out of fuel the rail would still be pressurized, but if I opened the fuel rail plug it would not be. I guess the pressure would drop a bit as I ran out of fuel, but perhaps not as much as if I opened the plug.

Still does not make sense that the pump should not self prime or that I can blow back into the tank from the rail supply line.

I'll try to use a fluid pump to prime the system tomorrow or something and report back.

This 'no-start' is really teaching me a lot about this car!

Neil Deshpande

1.2gees · 1.2gees's Garage

I cannot remember if your car has the dual pump set up or not. If so the in tank pump may have gone bad.

Neither pump should need "priming".
Ahmet

Pike · 04-22-2003, 10:33 PM

Quote:

Originally posted by neildeshpande
It is the square cross-sectioned 'tube' that runs along the top of your cylinder head....
All gasoline cars should have a fuel rail.

Neil Deshpande

I know what injectors are, but did not know what 'fuel rail' was. (I am still not sure if I have one) Good luck on the diagnostic though.

P.S. "Square tube" !?!

neildeshpande · 04-23-2003, 11:54 AM

Quote:

Originally posted by 1.2gees
I cannot remember if your car has the dual pump set up or not. If so the in tank pump may have gone bad.

Neither pump should need "priming".
Ahmet

Ahmet:

The in-tank pump, the only one on this car, is new. I just put it in. Also, this is the same pump that pressurized the fuel pump just a week ago and has been run, maybe, 3-5 mins since. I think it is probably OK.

I'll have more time to work on the car this weekend.

Neil Deshpande

1.2gees · 1.2gees's Garage

Why did you replace the pump so recently? (And with a new one?) Did you have fuel troubles prior to this?

Let me/us know what happens.
Ahmet

neildeshpande · 04-23-2003, 03:05 PM

Ahmet:

When the car started dying intermittently, while with the PO (my brother), I recommended R&R of the fuel pump as that is what my Bimmers did when their pumps went at about the same mileage (same pump manuf.).

Anyway, my brother gave up on the R&R and shipped the car to me instead. I worked on it and found a no-spark condition. I put in the new pump I had sent him anyway and a new filter, which I had also sent him earlier. I do this on all my Bimmers preventively around 120k miles as I don't want to lose power on the highway with a semi-truck behind me at 90mph. Know someone whose wife died that way.

When I got the car, it had sat around 8mo with the fuel pump line from the tank off. So, tank was drained 100%. The rail may or may not have been pressurized when I got it, but it surely was after I cranked it a few times as I got high pressure fuel spewing out when I removed the injectors to check spray pattern when it would not fire with strong spark. It was running on starting fluid, however, which caused me to suspect the injectors.

The rest you know.

Neil Deshpande

Roger Hall · 04-23-2003, 03:50 PM

Quote:

Originally posted by Pike
I know what injectors are, but did not know what 'fuel rail' was. (I am still not sure if I have one) Good luck on the diagnostic though.

P.S. "Square tube" !?!

On your 77 I belive that you do not have a fuel rail. Instead you have individual fuel lines that run to each injector. Other cars have a single fuel line or fuel rail that all the injectors conect to. With CIS the fuel distributor and fuel lines are the fuel rail.

3sonfather · 04-23-2003, 04:20 PM

Neil,
I've been following your saga. FRW has a point; you probably got a big gulp of air in between your pump and your tank. I suggest you loosen the connection aft of the fuel pump and allow a trickle of gas through, purging most of the air. Good luck and keep us posted on bringing your car to life.
Scott

neildeshpande · 04-23-2003, 06:04 PM

Quote:

Originally posted by Pike
P.S. "Square tube" !?!

I _did_ put it in quotes for that reason!

Neil Deshpande

neildeshpande · 04-23-2003, 07:37 PM

Gruppe:

After some thinking I recalled that I'd had trouble putting back the hose from the tank to the pump while keeping it (1/2" inner dia) from kinking. So, I reached under the car, dekinked it by crushing it with channel-locks, put two zip-ties to hold it unkinked and cranked the car . . ..

Vrooom! Hurray!

Reminds me of something from H W Longfellow's "Village Blacksmith".

Toiling,--rejoicing,--sorrowing,
Onward through life he goes;
Each morning sees some task begin,
Each evening sees it close
Something attempted, something done,
Has earned a night's repose.

I cannot thank this board enough for the detailed pointers and for those who simply followed the link and provided encouragement. I hope I can help you guys back as I work on the car more and more.

Neil Deshpande - heading for some of "Nature's second course"!