senihele

Hey guys,

Short story: I think my fuel pump is bad - have I looked into all the other possibilites?

Background: So, my car has had trouble starting in the cold lately (usually anything below 30ish degrees f). It would crank and crack, but only if I really mashed on the gas petal could I get it to start. With the warm weather coming, I thought I wouldn't have to worry about this problem for awhile, but after a week or two without problems, the car started giving me the same issue even in warm weather. Now it won't start at all.

What I've done so far: I've isolated the problem to the fuel system. The car will start with starter fluid, but dies after a few seconds (after it burns through the starter fluid). I opened up the gas line before the FPR and it was bone dry. I have tried jumpering the fuel pump terminals and using a backup DME/Fuel Pump replay, but nothings seems to get the fuel pump started.

So the issue is 1) a new fuel pump is not a trivial expense and 2) the car is currently backed into a garage with the right side a few inches from the wall and there isn't really anywhere I can push the car, so accessing the Fuel Pump is also going to be quite a challenge.

Basically my question is this - is there anything else I can or should test at this point, or should I go ahead an buy a new pump and try to get it on somehow? It could be the fuel filter - but I can't imagine there would be *NO* gas in the line because of that. Is there a way I can check if power is getting to the fuel pump without having to figure out how to get down there? If I do need to get back there, should I test the power and how would I do that?

Everything I've read indicates if there isn't enough flow before the FPR, replace the fuel pump but I just want to see if I should check something else first.

Thanks!

Funn944

Mashing the gas pedal to the floor will not have any effect unless the engine is already flooded with gas, which is very unlikely if your fuel pump is not working. Our cars do not have accelerator pumps like a carburator (push the pedal down fuel squirts into the intake). If your car will start with spray fluid, more than likely your not getting fuel into the rail. Bad relay, bad connections in the fuse box....ask me how I know.....bad fuse, bad pump, plugged filter or pickup. Broken wire between the fuse box and the pump ? Is there actually gas in the tank (bad fuel level sender showing gas when there is non ?)

blown 944

Check the fuel pump fuse.

If it keeps blowing for no reason the O2 sensor may be shorting. PorscheDoc informed of this and I still thank him for that b/c being it the O2 I may still be looking.

peanut

I suggest you remove the electrical connector from the pump and clean the contacts and earth connection and try jumpering the DME and test again.

If no joy then disconnect the pump electrical connector and connect the pump directly to the battery. If the pump doesn't start pumping give it a good thump or two.

If it still doesn't pump then the likeihood is your pump has died.
If so I'd probably it remove and strip it to check the internals to see if I can fix it.
You don't have to replace it with a Porsche pump necessarily. Plenty of aftermarket pumps that can do the job. I think you'll need about 1.8lts a minute flow rate for an S2 less for a Lux.

If your fuel is draining out of the rail then the anti backflow valve in your pump is probably stuck in the open position which would mean the pump will struggle to flow sufficient fuel to maintain sufficient fuel pressure for the injectors to operate. Your injectors could be sticky too

senihele

Thanks everyone for the quick responses -

@Funn944 Rapidly pushing the accelerator definitely did help start the car, but interestingly it seemed more lifting off the accelerator very quickly helped the car catch more than anything. I have no idea what this would mean. I've checked and double checked the fuse. I tried a backup relay and jumpered the terminals directly.

@blown 944 I should have mentioned in my original post, but I have checked the fuse - pulled it out and examined it. Looks good. I don't have a spare but I could swap it with another, but I did inspect it pretty closely.

@peanut Thanks for the suggestions. I'll have to play around with it directly this weekend. I guess I was hoping there'd be an easy answer, but doesn't seem to be the case. Even if there were a problem with the anti backflow value, I should be able to hear this pump working, yes? I've never listened for the pump sound before now, so I don't really know what I'm listening for, but it seems completely silent back there, even when underneath the car.

peanut

If you put a jumper between 30 and 87b under the DME relay you should hear the fuel rushing through the fuel rail and FPR back to the tank, well I could on my S2 anyway . If the fuel system has lost all fuel there may be a jolt as the pump re-pressurizes the system. I was surprised how much of a jolt I got in my car last w/e before I finally got my S2 going after 4 months of non running .

senihele

Hey all,

I could really use your help on this - I'm now pretty stumped. I got ahold of a spare fuel pump to test with. I swapped out the old one with the spare yesterday, but still have no gas before the fuel pump regulator and the pump itself doesn't seem to be on.

I checked the terminals at the fuel pump and I'm barely getting any current. I cleaned the batter terminals that doesn't seem to be a problem. I double checked the fuel pump fuse and have a new fuel pump relay in. I really can't figure out why the pump would not be getting current, or how that would have caused the fuel pump to work on and off over the past few months.

Any thoughts?

N_Halbert

You still didn't say you had check your DME relay. This controls the fuel pump. If it is working correctly, when you turn the ignition to the on position you should hear a wine from the pump as it comes up to pressure before starting.

See Clarks-Garage - FUEL-05, DME Relay Technical Information and Testing
http://www.clarks-garage.com/shop-manual/fuel-05.htm

blown 944

It only gets voltage when cranking over unless you have the 3 wire jumper installed. Was it installed when you were testing??

If so there is an electrical problem pre pump

if not then try to use the jumper and test it (pump terminal) for voltage

peanut

i think there is a picture somewhere on Clarkes on how to jumper the DME. its very simple. Remove the dme relay get a 6" piece of wire with bare ends. Shove one end in the hole marked 30 and the other end in the hole marked 87b your pump should start pumping immediately and won't stop until you remove the jumper.

I am not sure you are testing the fuel at the right place. You should remove the bleed screw which is half way along your fuel rail . Do you know the which is your FPR and which is the fuel damper and where they are on the rail? its different for different models.

If you have a poor supply to the pump then do as I first suggested. Remove the supply leads and run a pair of wires to the pump from the battery. At least that will tell you if you have a 12v supply problem.
Have you made sure that the pump has a good clean earth connection.

Have a look at the fuel system schematic on Clarkes garage it will give you a complete overview of the fuel flow. It comes from the tank to the damper first then to the fuel rail and injectors then to the FPR and then back to the tank. At least that is the flow on an S2

You need to try these suggestions and answer our questions if we are going to be able to help you.

has anyone found out which model the op has yet ???

senihele

Hey all,

Thanks so much for the quick replies. I've been trying to fix this problem for two weeks now and not having a running car is really starting to disrupt the rest of my life. I'm going to run through a number of the suggestions made, but I wanted to leave a few details:

The car is an 87 NA. I'm testing fuel flow toward the forward (relative to the car) part of the fuel pressure regulator. I'm using this (http://www.clarks-garage.com/graphics/fuelrail_left.jpg) diagram on this (http://www.clarks-garage.com/shop-manual/fuel-07.htm) page to determine the location of the fuel pressure regulator and opening the line to the left (relative to the positioning in the diagram). The line at this point is essentially empty.

Regarding the DME relay, I inspected the old one, but also had a new one that I tried. Currently they new one is installed. I attempted to start the car with the new one, but had no gas at the point I indicated above (before the FPR). Since swapping the pump with a spare, I have not tried to start the car, but was under the impression that the fuel pump should start when the key was turned partially. I can't hear anything or see anything in the line.

I also tested the voltage of the battery, which only seems to read 9.56 volts at this point. My friend who has been helping me through a lot of this suggested the voltage may be insufficent to trip a number of the relays and get power back to the fuel pump. I did try to jump it with the old pump installed, but haven't since I swapped pumps. I am going to try to jump the car tonight and see if I can get anything.

I am testied voltage on the fuel pump not directly on the pump terminals, but just before where there is a connector in the wire (I'm not sure what the technical term for this is).

Also, I'm a little confused - N_Halbert, you say I should hear the fuel pump at the on position, but blown 944 you say that it will only start when cranking? I'm not sure if I understand correctly.

I don't have the wires for some of the suggestions here (sorry, a little new to this kind of work). Tonight I'm going to try to jump the car to see if it is a voltage problem. I can also make sure I'm checking the fuel line at the right point - it looks like that might not be the case (although either way I'm not hearing the fuel pump turning on). Tomorrow I can buy some electrical supplies to do some of the other testing.

Thanks again for all the help. I really appreciate it.

senihele

Hey all -

Jumping the car this time worked! Since I tested it by jumping the car from two different good batteries before (including a tow truck), the problem does seem definitively fixed. I'm concerned that either the FPR or filter need to be replaced as well, though, and that they may have caused the occasional other problems earlier and led to the fuel pump failure.

Also, I suppose there is an outside chance something else we did fixed the problem. What is the best way to definitevely test to make sure the pump actually went bad?

Thanks!

peanut

the wire just needs to be any insulated wire ? how difficult can it be to take a piece of table lamp cable and strip the ends ?

The car has to crank over at a certain minimum revolutions in order for the crank sensor to pulse the DME which controls your pump relay and injector pulses. Basically all you had to do was put a 3" piece of coat hanger or wire into the two terminals like I suggested and that would over-ride everything and operate the fuel pump.You would then be able to prove the pump works and test the amount of fuel it flows .

I cannot believe this turned out to be a flat battery wtf ??!..

I strongly suggest you put the car in a Porsche garage and let them sort it before you inadvertently damage something.

senihele

@peanut - thank you for all your suggestions. To be clear, the original problem was not the battery. I tested the old pump double jumping off of an industrial strength battery on a tow truck with a brand new DME relay installed and it didn't work. After the fuel pump change, jumping off an old mitsubishi mirage starts it up right away.

Changing out the fuel pump seems to have been a success. The only issue was I ran down the battery during my earlier testing (after trying to jump it), so when I went to test the new pump it didn't work, but a jump fixed it.

This is my first serious repair attempt and it has been a very postive experience for me - I correctly diagnosed the orginal problem and successfully performed the repair (swaping out the fuel pump). When this didn't work at first, I managed to figure out that something had changed, tested the battery and noticed it was now low. Now everything works.

I'm not sure why you'd want to discourage me just because I didn't have all the right electircal equipement (no, I have no spare wire laying around, but said I would pick some up immediately and follow your suggestion) or realized I could use a coat hanger. I appreciate all your help, but understand I am still learning and all I can do is be as open to suggestions and advice as possible. The subject of this thread was, afte all, "anything else to test?" so your suggestion was exactly what I was looking for.

blown 944

I agree that it was the pump.

No the FP will not get power unless the starter is turning the engine over or if you have a jumper wire installed.

You did the correct thing to fix it however teh steps taken to diagnose were a little backwards.

ie..
you should make a jumper wire and keep it in the glove compartment
use the jumper to eliminate items for future diagnosis (DME relay, S/R sensors etc)

if the jumper were installed and it was getting power (at the FP terminal) that would have told you that the fuel pump was bad.

I also always recommend having a fuel pressure gauge on the rail as it can help diagnose items like s/r sensors, injectors etc..

regardless it is fixed so nice job