Fuel to the injector rail but car is fuel starved, won't start

[Chells_88ix]

We replaced the head on the '88 ix with another that was removed from a running motor so I wouldn't think there would be an issue. In order to make it easier to get the head off the intake manifold, fan, radiator and air box were removed. Now we have everything back on where it looks to go and cannot get the car to start.

It cranks but does not appear to be getting fuel. We just replaced the fuel line that runs from underneath on the drivers side to the fuel rail after the previous line failed at the rail and popped. Tried starting after this and she still won't go beyond cranking. Pulled the plugs at each end and they are dry, no gas smell or anything. We double checked the electrical plug that is attached underneath the intake, the larger twist plug and it seems to be connected tightly. Seems like the injectors are working (based on the easy test of putting a screwdriver to the injector while cranking and listening to see if you can hear the click, it was in the Haynes manual) but we have yet to test them with a meter. This is the first German car we have worked on so any ideas? Prior to the head being changed the car ran, no apparent issues with the fuel system as the problem that created the miss was the broken rocker arm (or so we thought). I have read the Bentley, Haynes, and Chilton manuals throughout and cannot find where to look next. Any ideas would be appreciated. Thanks, Chelle

[jlevie]

If you have spark and can hear the injectors clicking when cranking over the engine and have dry plugs, the problem just about has to be a lack of fuel pressure at the rail. That might be a bad fuel pump relay, bad FPR, bad pump, blocked line, or even mis-connected fuel lines. Force the pump on by jumpering the relay contacts at the fuel pump relay and start trouble shooting.

[Adrian_Visser]

Are you 100% sure that the injectors are opening? There is a ground strap at the back of the valve cover that the injectors use, make sure that is connected, of course if they are opening that ain't the problem.

[Chells_88ix]

It sounds like they are opening, but there is a delay before you can hear the clicking. Should they start clicking right after the key is turned over? At first we didn't think they were working but we kept listening and finally they started clicking. I will double check the ground strap as I don't remember seeing that. Pretty sure that the fuel line to the injectors is correct since it actually failed and blew out so we replaced it and traced it back to where it connected to the underside of the car.

[Spinning Tires]

I think you have the fuel lines crossed. The supply line goes in the back and the return line goes in the front on the regulator

[Adrian_Visser]

I'm not positive all e30's have that ground strap but my '84 eta did. having the fuel lines crossed is definitely a high probability.

[xLegendOZWest]

are your lines backwards? the supply line goes to the side of the rail the regulator is NOT on. that might be why your line popped due to the regulator keeping fuel from entering the rail. worked for me so i thought id mention.

[Chells_88ix]

Well I am sure that the correct one is on the rear of the fuel rail, because when we went to remove it we had to cut the hose because it would not pull back off of the connector at all, may have been because it was 1/4" line since we couldn't get the 1/4" back on without it failing so we changed that one over to 5/16" and ran new line back to where that originated.

Don't smack me but how many fuel lines would have been removed to take the head and intake manifold out? Maybe I need to get a recount and go again. We followed the Bentley but the head ended up being off the car for a few months due to it being too cold in the garage to work.

[jlevie]

Early cars have the inlet to the fuel rail at the rear of the rail and late cars have the inlet near the front of the rail where the FPR mounts. The return line attaches to the FPR, but both the supply and return lines run next to each other under the car. It would not be hard to wind up with those hoses swapped.

Pull both hoses and direct them into a gallon container. The jumper the fuel pump relay and see which one delivers fuel. Connect that to the rail and the other to the FPR.

[Chells_88ix]

Ok, I have pulled both hoses and I had them on correctly as the one that puts fuel out is the one connected to the fuel rail. Looking at the Bentley it said you could check the fuel coming out of the back side of the fuel pressure regulator, when I took the lower hose off and tried it nothing came out at all with the other hose connected to the rail. Is that normal? Any more ideas is greatly appreciated as I would love to see if this car actually runs again.

[Spinning Tires]

If you have the return line disconnected from the regulator and the supply line hooked up to the rail and you turn the fuel pump on, you should definitely have gas shooting out of the regulator.

[jlevie]

Ok, I have pulled both hoses and I had them on correctly as the one that puts fuel out is the one connected to the fuel rail. Looking at the Bentley it said you could check the fuel coming out of the back side of the fuel pressure regulator, when I took the lower hose off and tried it nothing came out at all with the other hose connected to the rail. Is that normal? Any more ideas is greatly appreciated as I would love to see if this car actually runs again.

That's is not normal and would suggest that the pump isn't producing normal pressure or that the regulator has failed in a shutoff position. The clue as to which would be to check the pressure at the inlet of the rail by tee'ing in a pressure gauge.

[Chells_88ix]

Would your best guess then be that a new regulator would fix the issue? The fuel pump seems to be working since it pumps the supply line freely.

[Adrian_Visser]

That sounds really weird, so fuel is coming out of the inlet hose that connects to the back of the fuel rail with it disconnected and the pump running, but with with it connected to the rail no fuel is coming out at the front of the rail?

If the injectors are opening the fuel would still be released into the engine and the car would probably flood itself or run super rough because the fuel pressure would be too high at idle. Something is funky here.

[Spinning Tires]

I still say the fuel lines are swapped ha ha