Fuel Pump, Relay? Help!

[Quinthirty]

My car happens to exhibit the following symptoms, and I need the help from you experts.

1. It smells like gas in the engine area when left overnight.
2. It won't start if the car is left under the baking sun for a period of time. But it will start if I'm parked under a roof, though it might take a few clicks if its a hot day.

3. The car cranks really well, but there doesn't seem to be gas in the fuel rail as it will just continue cranking, or seem to start, and yet die again after a few sputters. Or upon starting (especially when cold), idle a bit, and die.

But once she runs, there's no problem. I don't stall on the road (yet). She has a bit of a rough idle, and at times the idle goes around 800-900rpm. MPG sucks at 10-11MPG (yup, not a typo)! No fuel leaking anywhere.

1. Bad fuel pump?
2. Bad fuel relay?
3. Dirty tank?
4. Vacuum leak?
5. All of the above

Would appreciate some guidance on how to test, and how to go thru a process of elimination. Thanks!

[7pilot]

You have a rotted fuel line. From the scent one can estimate that it is between the firewall area and the fuel rail on the engine.
The car won't run well as the leak causes a loss of fuel prime and a loss of pressure.
The fuel lines are metal under the car and run on the inside of the frame rail. Once in the engine compartment, they are rubber as thee run up the bend of the frame rail. they are rubber up to the fuel rail.
Continuing to drive a car with a fuel leak in the hot engine compartment is not safe.
The leak should be found on a cold car by looking at the driver side of the engine and chassis.
If neat fuel never hits the ground then the leak is above the engine which gets hot.

m

[jlevie]

It sounds like you have two problems. There is a fuel leak that is causing the gas smell and there are intake leaks or other problems with the engine management system.

Do not drive the car until you find and fix the fuel leak. The risk of an engine bay fire is just too great.

[Quinthirty]

Thank you, gentlemen. I won't drive it til I find the leak.

[Quinthirty]

I did the following things tonight just to start the process of elimination on the fuel leak.

1. Checked the fuel lines and hoses
2. Checked the charcoal canister
3. Checked the purge valve.

Since the smell of the gas is coming from the engine bay, I checked all the fuel lines and found that the one leading to the fuel rail is a bit on the soft side. I noticed that when I pressed on the other lines, they were thick and still malleable (not brittle), but the fuel rail line that starts beside the FPR going down, is starting to balloon. I guess this one is the culprit. Otherwise, there are no moist fuel lines, or anything that shows little cracks or signs of brittleness.

2. Checked the charcoal canister, and the connections from both the purge valve and the return seems ok, but still unsure whether this is leaking or not.

3. Checked the purge valve, and followed the Bentley instructions, and this also seems to have a problem. Based on the Bentley, I removed the connection from the throttle, and switched ignition to on so as to hear whether it was clicking or not. Manual says it should, but I didn't hear any. Only the ICV was sort of "buzzing" faintly. Second instruction of Bentley is to test for voltage, and this is where I got confused, because this is what it said:

"On models with Motronic 1.1 , the bypass valve hose routing is slightly different. See Fig. 4-21 . With the ignition off, remove the valve. Do not disconnect the harness connector. Turn the ignition on and check that the valve makes an audible click. If the valve does not click, remove the harness connector. Using a voltmeter, check for voltage between the connector terminals. With the ignition on, there should be approximately battery voltage.

1. If there is voltage, the valve is faulty and should be replaced.
2. If there is no voltage, then there is a either a fault in the wiring to the Motronic control unit or the control unit is faulty."

Isn't it confusing to read that either way, there is something wrong? There was no voltage by the way...But I'm still confused whether something is faulty or not.

What else should I check?

[jlevie]

The evaporative control valve and charcoal canister is unlikely the cause of a fuel smell.

Just because of age, replace both of the soft lines. You must use hose rated for fuel injection service (5/16" or 8mm) on the high pressure side. You can use ordinary fuel hose on the low pressure side to save a bit of money. Once the hoses have been replaced, jumper the fuel pump relay and look for leaking fuel.

[Quinthirty]

Thanks, Jim. I will definitely replace it with correct specs. I will also look at the lines again. I've already looked at the lines from fuel pump and sender unit (mine has left and right pump and sending unit), and the hoses looked new and dry. I've also looked at the under carriage up to fuel filter and it looks new as well. The only ones left are this fuel rail hose, and the 1/4 inch one from the fuel cap to the tank (braided).

The evaporative control valve and charcoal canister is unlikely the cause of a fuel smell.

Just because of age, replace both of the soft lines. You must use hose rated for fuel injection service (5/16" or 8mm) on the high pressure side. You can use ordinary fuel hose on the low pressure side to save a bit of money. Once the hoses have been replaced, jumper the fuel pump relay and look for leaking fuel.

[Quinthirty]

I've finally changed the fuel line to the fuel rail, and it has eliminated the fuel smell of the car.

But I haven't solved the starting issues. Here's the situation:

1. Car starts well when cold / parked overnight.
2. When using the car, and its parked a few hours (engine still hot) car will experience the following:
a. car sputters to a start but dies, or,
b. car just cranks, but does not start at all. There's spark, but there's no fuel at the fuel line from the rail. It would take me 5-10 starts to get her running.

What I've changed before this happened.

1. spark plugs
2. oil
3. oil filter
4. fuel filter
5. ECU from a 152 (for a 320i) to 173 as it was installed with the wrong one, as it was running rich. The thing is, it was starting well with the wrong ECU.

What are the possible causes for this?

Should I:

1. Get another ECU just to find out if its the DME?
2. Coil, because it happens when the engine is hot? Rotor?
3. Fuel pump?
4. Fuel pump relay?

What else should I test?

[StereoInstaller1]

Have you done fuel pressure testing? The Bentley has a decent flowchart to help diagnose this stuff...but when you find it, post it up, please.

[jlevie]

Tee a fuel pressure gauge into the supply line to the rail and connect a test light to fuse 11. See what the pressure is the next time the engine fails to start. If the pressure is low, but the light is on the problem will be with the pump. If the light isn't on, the fuel pump relay could be bad, the DME may not be getting timing data, there could be a problem with DME power or ground, or the DME could be bad. A check for spark will help in the diagnosis.

[Quinthirty]

Thanks, I'll get to it within a week.

[5Toes]

Maybe your coolant temperature sensor is causing the hard start?

[Quinthirty]

Car acted up again tonight. This time it was worse. I parked the car for a good 30 min in the late afternoon, and when I went back to the car, the car started (one click), and revved it to around 2k, but when I brought it to idle, car sputtered and stalled. Cranked it maybe 5x, this time, priming the pump for a few seconds of ignition (switch on and off 5x), and it started. This time, really revved it to 2k RPM hoping to stay there. However, car sputtered again and died.

Now I was worried. I was thinking that maybe fuel pump is gone...

So I popped the hood and immediately checked on the fuel pump relay connections. I noticed of late that the terminals where coming lose as I try to push them from underneath and ensure that they're snugly fit. I need to replace this (perhaps you could recommend? Relay terminal locks are broken and brittle.

Anyway, I finally got to start it after 20x and a prayer...Got home, and as I was backing up the garage, I noticed that when I switched off the A/C compressor, idle went down and struggled to a sputter and died. This time, it didn't start. Just cranked, with seemingly no spark.

Conducted a test of both fuel pump relay, and the fuel pump based on Bentley. (No fuel pressure tester at home). There was voltage at the fuel pump 30 and ground terminals. Also tested fuel pump for continuity, and it was ok. Checked fuse 11. Still no start. Exchanged the fuel pump relay with the ABS relay beside it, and it took one click---vroom!

I'm not confident though. I will replace the relays soon, and maybe even the terminals as they're brittle. Hoping to conduct fuel pressure test, and fuel pressure regulator tests next...

I only have a hot start problem. It starts well in the morning.

Anything else I should check?

Sorry, Jim, haven't done all your tests yet because of lack of equipment. Shops are full too, and they want me to leave my car with no guarantees when the work is going to be done, so I DIY. Waiting for my DME to arrive. Found a smoke machine I can rent, but still in the hunt for a fuel pressure gauge.

[jlevie]

A fuel pressure gauge is easy. Go to Lowes, Home Depo, etc and get a 0-60psi gauge (like used on water systems), a 1/8NPT pipe tee and a couple of 1/8NPTx1/4" hose barbs. You really need 1/8NPTx5/16" hose barbs, but those won't be easy to find locally and the 1/4 barbs will work. Then go to an auto parts house and a few feet of 5/16" fuel injection hose and some clamps. Assemble and you now have a fuel pressure gauge.

[dnguyen1963]

"Exchanged the fuel pump relay with the ABS relay beside it, and it took one click---vroom! "

Are these relays interchangeable?