fuel pump? your advice is needed!

vital-transform · 02-26-2004, 08:46 AM

I need your help guys!
my 88 924S stalled on me 2 times the other day while driving at about 35 MPH (auto trans) the sensors are all new as are the timing and balance belts dme relay cap plugs fuel reg idle stabilizer afs tps- all new
and the car has been running GGGreat! today I am driving my buddy to the airport and it dies at a red light (normal operating temp) cranks but wil not restart...I get out the tools the car has good spark..
I popped off the distributer cap the rotor looked good and I scraped some gray rust off the inside of the cap contacts (cap is in fact a year old)
I checked the fuel pump fuse and it was good (the left high beam one was bad so I changed it#3)
so I changed out my new DME/Fuel pump relay for the old one and still cranks but no start?
Looking for vacuum leaks but all looks good
got out my blanket and took a look at the fuel pump looks like it has never been touched, I tapped it with a screwdriver and wiggled the wires at the connections.... starts right up!!!
and now drives fine???
do I change the fuel pump immediatly?
or get the pump and keep it in the trumk and then check out the wires and connections going to the pump?
This car has 85,000 miles and looks to me the pump is original.
next question...best price on a pump is from where?
I useally use Vertex and am checking out Pelican as we speak
Thanks for your help guys
LOL (love)

vital-transform · 02-26-2004, 08:54 AM

vertex has rebuilts for $95. and both PPand vertex get 189 for the new ones
what's the word on the rebuilts?
anybody used one?

and how about the check valve?
anybody have any check valve experiences or coments?

Zero10 · 02-26-2004, 09:20 PM

I would say it's most likely the connections. Pull the connector, clean all the contacts and put er back together.
They are most likely corroded.

Although it could be the pump itself, check out the connection first, it's cheaper to fix.

SoCal Driver · SoCal Driver's Garage

I concure on cleaing the electrical connections at the pump.

You can run the fuel pump by itself by using a jumper from aux fuse #2 to #3. This is the open eight fuse block. Count from the drivers door. Fuse #2 is the fuel pump. Fuse #3 is the one of the fans on the radiator and is always hot.

Using an aligator clamp jumper on the fuses is easier than pulling the DME relay and trying to stick a jumper into it's slots.

Check out these resources:

www.clarks-garage.com

and

www.frwilk.com

There is also a technical section to this web site www.pelicanparts.com

vital-transform · 02-27-2004, 02:36 PM

thanks guys ...I am under the back of my car tomorrow AM will let you know what I find!
GT

vital-transform · 03-02-2004, 10:45 AM

thanks guys ...again
Ok the pump will run when jumpered acrost the 2 and 3 fuse ala Socal's advice...the connections are have been cleaned and look good on the fuel pump itself the pump runs when jumpered and fuel is getting to the dampner / rail / fpr.
The car will run but dies in a few minutes... if I then jumper the fuel pump I can get it restarted but then it will die in a few minutes?
I am going out now to check the reference and crank sensors for debris? is that a possibility?
car gets good spark and cap and rotor look good
back in a few minutes!!

vital-transform · 03-02-2004, 01:07 PM

pulled the back sensor ...it had a speck of black debris in it , put it back in car fired up and ran for a good 20 minutes, after a test ride the car stalled on deceleration, wiggling the wires near the sensors brought it back to life and I could induce a stall by moving any of the wires in that general area???... the positive battery cable runs right near there and mine seems to have a lot of play where it connects to the harness just below the oil filler? has me concerned? anybody ever change one of those?
The sensors were both replaced about 2 months ago...but they are used...I am thinking that maybe I should replace both with new ones?
any thoughts and/or good sources of new ones?
the bracket has never been moved so I don't think it's about adjusting them as the car was running great?
I am going to teach my 9 year old how to change the sensors (smaller hands)

SoCal Driver · SoCal Driver's Garage

Get a few pull ties and pull the cables to one side or the other till it runs with out stopping.

How is the DME realy?

vital-transform · 03-03-2004, 06:33 AM

I have swapped the DME relay between the new and old one and these symptoms will occur with either...so I think the relays are OK.
You know how these sensor wires are kind of stiff, I am concerned that they may need to be replaced with new ones?
I do have 4 sensors total all are used, do you think I could hook them up to a multimeter and wiggle to detect any defects and then use the undamaged ones?
the car runs good, today I will pull the other sensor to check for debris and then move the sensor wires around to see what gives with their condition (twist ties etc...)
looking back, the only thing that has changed about the car and its setup is I changed the oil...and It looks as if some oil splashed on the front sensor (the one I will look at today)

SoCal Driver · SoCal Driver's Garage

Check the sensor clearence too. 0.8 mm or about 1/32".

A hair thinner than a dime!

vital-transform · 03-03-2004, 08:25 AM

yeah I am going to convert the worse sensor into a gauge,
Ok I pulled the front sensor...no major debris but a film so I cleaned it and reinstalled, then cleaned the contacts on the plugs with contact cleaner and also any spilled oil on the sensor itself. I checked the routing of the sensor wires and locked them down. runs good and I am not able to induce a stall by manipulating the sensor wires!
I am off for a test ride.......

vital-transform · 03-03-2004, 12:04 PM

test drive did not go so well!
konked out at a stop sign about a mile and a half from my house...would not restart?
I checked the wires and connections nothing...if I jumper the fuel pump via 2 +3 fuses it will run until it loses fuel 2 -3 seconds I switched dme relays nada...
I decide to change out the rear sensor as I have a spare with me ( by the side of the road!)that has no effect either
at this point I am thinking DME?
I called my wife to pick me up...I am now thinking...what is on the other side of those sensors?? maybe a magnet on the flywheel? I rolled the car in neutral and then threw it in gear as my wife pulls up I turn the key and the thing fires up!!!???
I am so confused?drove fine on the ride home but I want to check it out a little further before I hit the highway?
Does that sound like a real possibility? or could this be some kind of intermittant DME thing? does that or can that happen? Ignition switch a possibility?
anyway I am approaching in this direction let me know if I am wrong.....
got spark from coil to cap and to plugs no problem there...if fuel pump is jumpered it will run until fuel runs out so I am thinking that the pump is not getting a signal to pump when the ignition switch says start? (next time I will have someone else crank while I listen to the fuel pump)(it useally konks out while decelerating or just stopped?)
when it runs it runs normally so I do not think it is the DME? could the fuel filter be clogged / stuck up? (nah, plenty of fuel runs to the rail when jumpered) I think that either the pump is not getting a signal to pump or the injecters are not getting a signal to fire?
can the crank / flywheel magnets really be a possibility? ever heard of that?

vital-transform · 03-03-2004, 12:08 PM

I just had a starter put in by my mechanic about a month ago?
I don't like going to the mechanic can you tell

vital-transform · 03-03-2004, 12:15 PM

I am toying with the idea of having a DME test plan done by a Porsche dealer or specialist? I was quoted a price of $95. by a dealer on Long Island

SoCal Driver · SoCal Driver's Garage

Thinking break in wiring to the injectors. These wires go right over the sensor wires and plugs. You most likely are moving them when futzzing with the sensors. If you pinch the sheathing you can feel the splices. These are solderd and have been known to break. You can take a test lead from the positive on the battery and connect it to one of the injectors and bypass these splices. Think it's the #1 pin (gray wire) but will have to check.

Next time pull the connector off of the #1 injector and check for voltage with the key on.

Best if you don't turn the key off when it dies.

Should have close to 12 volts on both sides of the connector when one or more injectors are still pluged in.

vital-transform · 03-03-2004, 08:47 PM

I'll check those in the AM and I am off to get a noid light....could the teeth on the crank that the sensors sense be a cause ? I am wondering why it would start after I rotated the crank/flywheel manually?

vital-transform · 03-05-2004, 06:16 AM

Got stuck again...looks to be heat related ...will start when it cools down then runs fine?
I am out again today with my multi tester and aligator clips....I am thinking starter solonoid circuit / DME / or the Fuel pump are acting up when they warm up? and/or posibly a broken / worn wire?(I am running through all the Clarks garage no start tests next time it occurs)
I am thinking of connecting a light to the fuel pump fuse so I can see if the pump is still getting power when this occurs next time?
If the pump is still getting power then it will mean replace the pump if the power to the pump cuts out it will be DME or related issue...wires etc...the DME relay I swap out as soon as this happens with no result...but power to the relay may not be there because of a bad wire etc...

vital-transform · 03-05-2004, 06:24 AM

oh yeah the ignition switch...can they get "hot" and cause problems I am also looking at replacing the electrical portion of the switch? not sure if thats a stop running when warm type of thing?

SoCal Driver · SoCal Driver's Garage

Still sounds like electrical problems.

If the starter engages and spins the engine then it's not the starter.

This leaves the DME, fuel pump, ignition switch and related wiring.

The DME controls the fuel pump relay. So when the engine drops below a set rpm the DME cuts off the fuel pump. You would have to see a monitor light go out before the engine dies.

I'm still concerned about the "wiggled wires". A broken wire in the injector harness or the special cables to the sensors will do this.

Did you try leaving the jumper on the fuel pump and driving it?

Did you try bypassing the 12 volt circuit to the injectors?

vital-transform · 03-05-2004, 09:00 AM

right now I just got a battery at radio shack for my multi meter, I hooked up a light to the fuel pump fuse so I can see when power to the fuel pump is interupted and then try to figure out why?
I have gone wiggeling more wires (sorry)this time I got underneath and took a look at the starter solonoid wiring thinking that the movement at the sensors and Positive battery cable lead down to the starter as well and the solonoid signal is required for the run signal to the DME...and I had the starter replaced at my mechanic this winter (foot of snow on the ground and 15 degrees)
anyway I am ready to: next time it dies I will check the starter solonoid circuit at the DME plug then the fuel pump itself, power to the injectors, power to the DME relay and the ignition switch.
I have been driving around town all morning and have not been able to duplicate the problem...but I am sure it will as soon as I try to head to work!!