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Discussion Starter #1
Are there any fueling system guru's out there? I just went out to wash my car and found that my 94 vert wouldnt start...Its my daily driver and ran fine without issues yesterday.

I have determined the fuel pump isnt turning on. I unbolted the banjo fitting on the fuel rail and there wasnt any pressure or fuel leaking when the key is in the on position, or cranking over.

Per the bentley I put a jumper wire between fuses #27 and #30 and still no fuel pump noise/pressure.

I also located the fuel pump relays but the bentley is a bit vague as to how to test it.

anyone know what the next step is?

The car has red series injectors/eprom/apc. I was wondering if the increased fueling needs from these could have faulted the pump?

Thanks in advance!
-Jeff
 

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Discussion Starter #2
I will be pulling the pump out tonight to test it. i was just going to order a new one today until I looked at prices $300.00-500.00 for a fuel pump :eek: .

I want to make sure the pump is bad before I dump that much on a new one.
Is there any better way to test it than hooking up a battery to it directly?
 

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Discussion Starter #4
Jim,

Is it tested by simply hooking up the +and- to the pump directly? (12 volts)
I tried bypassing the relays and testing it that way but it didnt have any effect.

Thank you,
Jeff
 

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If you just connect a battery to the pump, you eliminate all other possibilities.
That's not how I'd do it, but it's foolproof. You could test it from the fusebox, but I can think of several ways you could go astray.
 

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Discussion Starter #6
Thanks Jim,

I ran out of time yesterday and didnt get a chance to test it but I'll hook it up tonight to see if it works.
 

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Discussion Starter #7
Stumbling through the Benltey has taught me a lot about the LH fueling system in the last few hours and not to mention an insight into electrical schematics and testing ...lol.

Upon testing everything from the air mass meter to the fuse box, to the fuel pump, the ecu, injectors and main relays I think I have determined the culprit...

The pump checks out fine there just isnt any power getting back there. I traced the issue back to the main relay/fuel pump relay located next to the ecu in the passenger footwell. The main relay socket checks out fine as per the bentley but the fuel pump relay socket does not. I am assuming this means the main relay is faulty as power is not making its way to the pump relay.

Is there anyway to test the relay itself aside from buying a new one and pluggin it in?

I am running LH2.4
 

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shaverjeff said:
Is there anyway to test the relay itself aside from buying a new one and pluggin it in?
Of course there is.
Apply power and ground to the pull-down side of the relay, check for a circuit on the power side. It's best to check the power side under load. Your wiring diagram will clearly identify which numbered connectors are which.
 

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Discussion Starter #9
So there are some sort of moving parts inside the relay that should activate when power is added? I am assuming I'll hear an audible click?

I've never actually seen the inside of a relay to know what they do...
 

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Discussion Starter #10
Went to the the junkyard today and surprisingly there were a few c900's I picked up 6 or 7 relays at about $4.00

I replaced the main relay and fuel pump relay (where i could not get power when testing)

Success!!! Fuel pump kicked right on and car started right up...
Not sure what caused the relay to fail.

Perhaps its a side effect of the bov stalling issues?
Or related to the aftermarket apc/eprom/injectors???

Anyhow Its back on the road today and Ill see if its breaks anymore relays.

Thanks guys!
 

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Discussion Starter #11
Ok I went out to go for a ride and the saab wouldnt start again.
No fuel pressure, no power at the pump.

Fuel pump ran when I bypassed the relay circiut via the main fuse box. I checked the main relay. I had power there. I checked the fuel pump relay, I have power there, I bypassed the fuel pump relay with a jumper at pins 86 and 30 and the pump ran fine.

I tested all 5 relays I got from the scrapped thinking i could have possible grabbed a bad one :confused: They all check fine using a direct connection there was an audible click.

I popped two more relays in and the saab started right up...

I am baffled as to what is going on.

Im going to let it sit overnight and see if it will start in the morning.
Anyone have any suggestions???
 

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Discussion Starter #12
OK, so my next theory is.....

The car will not start or power the pump unless there is fuel pressure in the rail...If I bypass the pump circuit to run the pump and prime the system it will start up and continue to run fine. I can shut the car off and it will restart. If the car sits overnight I lose fuel pressure and it will not start again...

Is the car suppost to maintain fuel pressure all the time even over night??
Would this be caused by a failed fpr?
 

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shaverjeff said:
I will be pulling the pump out tonight to test it. i was just going to order a new one today until I looked at prices $300.00-500.00 for a fuel pump :eek: .

I want to make sure the pump is bad before I dump that much on a new one.
Is there any better way to test it than hooking up a battery to it directly?
Jumper it to run manually as per the Bentley manual but do NOT use a jumper wire that isn't fused. The fuel pump fuse is there for a reason! :cool: Then get a meter and check if you're getting 12 volts at the fuel pump, if you are, and the pump isn't running, then either the main pump is hosed, or the supply pump (if it's an 85+ car which use the dual-pump setup) had died or stopped working. You should be able to hear the main pump when everything else in the car is not turned on.

If you don't measure nominal 12 volts at the pump with the manual jumper correctly installed, check that there's 12 volts present on either of the plug-in terminals of the jumper wire so you know that the relevant section of the fuse/relay panel is powered properly and is delivering power to the location where the 12 volt wire to the fuel relay (it's a little different with a 16V engine) runs from.

If that's ok, there's a problem with either the +12 volt or ground wire to the pump. Check the ground wire first since it joins to the rear-earth point at the back of the central chassis member and it's easy to trace. if that's ok, then you'll need to work out what's going on with the +12 volt wire from the fuse/relay panel.

Assuming all the wiring checks out, and you still don't get 12 volts at the pump, the problem is not in the fuel-pump wiring but elsewhere in the electrical system but it could simply be a terminal that's come loose under the fuse/relay panel. There are a few multi-terminal distribution blocks under the fuse/relay panel and the fuel pump power supply taps off one of those.

Out of interest, my fuel pump switch box is something I created myself from stuff I had on hand. It also comes in handy as a way to 'tap' into a fused circuit and connect a fuse across a circuit for testing when there's a fault and have it in circuit with my meter. But that's just a side-benefit. I just pop out the clip-in fuse holder and connect leads to the connections on the fuse holder to hook in a blade fuse of the right amp rating for the circuit being tested.

Craig.
 

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Discussion Starter #14
Craig,

Excellent right up, thanks!

I have followed your instructions as well as the bentley's similar tests.

I have assumed the pump is ok and I am leaning towards a fpr issue. I can prime the pump by using the jumper wire then put everything back together and the car starts/runs fine. If the cars sits overnight it loses fuel pressure and will not start.

Itis my understanding that the line should remain "pressurized" when off to prevent vapor locking. This theory was tested when removing fuel fpr off the lo9cal junkers ;), they had plenty of pressure still. I have none. Unfortunatly my car is a 94 turbo vert and all the junkers were n/a and have a 3 bar fpr and different fuel rails connectors :(.

I am currently under the assumption I need a new fpr but I am curious if the fuel pump could start the car eventually even if the line wasnt primed.
 

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They only need to retain fuel pressure for 20-30 minutes; until the danger of vapor lock is past. If yours is not holding pressure, it would only affect hot starts. Loss of residual pressure is most often a fuel pump check valve, not the pressure regulator.
 

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Discussion Starter #16
oops too late I just ordered a 3bar regulator :D .

I thought it was odd that when I open my fuel rail there is no fuel there but even the cars in the junkers spray fuel everywhere when you open them up.

Is it possible to test the check valve? What does the check valve do?
I dont have the bentley handy but I'll give it a look tonight.

Thanks again Jim.
 

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shaverjeff said:
Is it possible to test the check valve?
Of course it is.
All you need is a fuel pressure gauge.
I don't understand why people are willing to "try" (read "buy") a new fuel filter, fuel pump, check valve, fuel pressure regulator, fuel distributor, fuel pressure accumulator, fuel system cleaner, injectors, cold-start valves, relays, temperature sender, auxiliary air valve, AIC, or ECU to answer questions a fuel pressure gauge will answer; and the gauge will work on any car.
"The fuel squirts out" or "the fuel doesn't squirt out" is not a valid test.


On one end of the fuel supply system, the fuel pressure regulator closes a valve that maintains pressure at the specified limit. At the other end is a check valve that keeps the fuel from running back into the tank when the pump is off.
 

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Discussion Starter #18
Jim,

I passed up a fuel pressure testing kit yesterday as I thought $40.00 was a bit steep for the kit. Of course I just spent $70.00 on a new fpr I probobly dont need.:roll: But my reasoning is that its nothing more than excuse for me to buy some more performance stuff. I have been running larger injectors, eprom, and apc for some time now and I'm sure the new fpr will compliment it nicely.

I am positive its a fuel pressure problem as there isnt a drop of fuel in the rail after the car sits overnight. (and its not leaking) Unfortunately I'm only smart enough mechanically to be dangerous so everything is pretty much trial and error on my part with guidance from guys like you and the Bentley manual.

I will pick up the testing kit tonight but wont it tell me what I already know, that the system is losing pressure? I was unaware of the check valve until now.

I am assuming the check valve is inside the tank and a part of the fuel pump?
I'll do my research when I get home tonight..Thanks!
 

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shaverjeff said:
I will pick up the testing kit tonight but wont it tell me what I already know, that the system is losing pressure?
It's normal for it to lose pressure overnight. It's only required to hold pressure for 30 minutes.
It is not necessary for the fuel system to be under pressure for the car to start. I was under the impression that your fuel pump wasn't running. What have you done to investigate that (other than replace the relay)?
A test light or voltmeter applied to the right place on the fuel pump relay (the ground side of the pull-down circuit) will tell you if the ECU is doing its job. That step won't cost you a dime.
 

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Discussion Starter #20
Jim,

I have tested the relays and relay sockets and I am getting the correct voltage at the fuel pump socket when cranking. And the correct voltage at the main relay with the key in the on position. This is strange because I dont think the pump is kicking on when I crank the motor over. It will however kick on once the car starts. The car will only start if I pressurize the system first by bypassing the relay and running the pump manually first. I have a garage helper tonight so I will be able to test for power at the pump when cranking, initially I assumed if the socket was producing power then the pump must be on when cranking but that may not be the case.

Thanks for consistantly providing input!
 
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