Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > 911 / 930 Turbo & Super Charging Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Help!! Fuel Relay Question.

Hello,

I have a weird dilemma happening with my 87-930. While reading this post, keep in mind that the car ran beautifully 1-week ago and then I tried to start it today and this happened.

When I take out one of the fuel pump relays, the other pump still works, and visa versa. When I put both relays in (which is normal) neither pump will even turn on.

I'm guessing that for some reason I'm not getting enough power (electrically) to turn on both pumps. What the heck could possibly be wrong.

1) Does someone have a wiring schematic that shows where the power for these relays comes from?
2) Would the over-boost switch cause this to happen if it fails?
3) What about a ground? Could a bad ground effect the ability for only one pump and not both come on?

Thanks for your help in advance. I purchased 2 new relays just in case and now probably do not need them. I wanted you to know so we don't think that is the issue.

Bryan
Old 05-02-2008, 04:31 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Found the problem. Is this OK???

Well,

So, I used an in line fuse connector (with the normal blade type fuses) and bypassed the oem ceramic fuse and added a 30amp (just to see) and both fuel pumps started right up and the car runs great.

Questions:
1) Is this OK?
2) Should I put a smaller amp fuse in the connector?
3) Why would it not work with the oem fuse anymore?
4) Could the 21 year old wires be corroding a little and require more current to travel through them to work?
5) Lastly, what amp fuse (10, 15, 30) is standard and should I just add a larger amperage?

Any help would be appreciated. If you need a photo for better description, please let me know and I will snap one.

Thanks,
Bryan
Old 05-02-2008, 05:29 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
wcc wcc is offline
Registered User
 
wcc's Avatar
 
Join Date: Aug 2005
Location: Michigan
Posts: 3,334
Maybe your alternator is getting ready to go? Has your Tach done anything crazy lately? I don't think running a smaller fuse is the answer. I'd check the charging system and see if it's working correctly first. Is the battery going bad? Ground Strap from the trans to the body?
__________________
Bill
Old 05-02-2008, 05:39 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
OFF THE BOOST PIPE NOW...
 
A930Rocket's Avatar
 
Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
Posts: 7,473
That's actually a Lee Rice electric upgrade that I did myself. Read the article for what fuses to use.

http://www.pelicanparts.com/techarticles/rice_ramblings/rice_ramblings-2.htm
Old 05-02-2008, 06:38 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Thanks

A930 Rocket: That is almost exactly what I did. Thanks for the tips

WCC: Question - If you read carefully above when I take out one fuel relay the other fuel pump will work. When I switch and leave the other one open, that one will work. All of this is done when my car is not running. When I install both relays, nothing works

Not sure how the alternator could affect this process when the car is not running?

Thanks,
Bryan
Old 05-02-2008, 08:38 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Join Date: Mar 2006
Location: Elk Grove, CA
Posts: 513
Send a message via AIM to Chuck Jones
Bryan: I bought the complete set of several volumes of the Porsche Tech Service manuals for the 87-89 930. It came with colored diagrams of all the various wiring circuits. I can burn off a copy of the diagram if you need it. I'll be headed down your way when I get my car back here shortly.

I'll fire you an email with the name of someone down your way who may be alble to help you out.

Chuck
__________________
1987 factory Slantnosed 930 Cabriolet/Guard's red
2002 Midnight Blue 996TT X50
1999 Iris Blue 996 (Dash fire burned and totalled 9/07)
Old 05-02-2008, 10:58 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Problem is back again.

Well,

I was driving with a Euro Sunday group (Most cars worth more than mine) and my car died again at a light. The fuel pumps would not come on when I turn the ignition on.

Can someone please supply me with the wiring schematic for the Turbo fuel pumps? I would like to find their source of power and ground.

Thanks a bunch.

Bryan

PS. I own an 87-930.
Old 05-04-2008, 03:31 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
wcc wcc is offline
Registered User
 
wcc's Avatar
 
Join Date: Aug 2005
Location: Michigan
Posts: 3,334
Ok, well I haven't run into this problem myself. Just trying to give you something to think about or check. Sorry if my last post wasn't too helpful. I don't have a wiring schematic, but what I would first check is to see if I was getting at least 11.5 volts to each fuel pump. If so, then I'd check to see if I have the same voltage at the relays leaving the fuse box. If I have the volts at the fuse box and not at the pump/s I'd start looking at what's in between and see where the 11.5v quits. Maybe check the ignition switch and/or the connections in the Engine compartment etc. This is how I'd attack it. Sorry I'm not more helpful on this one, just thinking how I would try to figure it out if it was me. If nothing else consider it a free bump for the Monday crowd....
__________________
Bill
Old 05-04-2008, 05:17 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Thanks!

Bill,

That is very helpful and I appreciate your help. I am planning on doing exactly that but have to wait for some extra hands and a volt meter that my fellow "pelicany" has.

I will keep updating as I progress in hopes that I can find a wiring diagram for the fuel pumps and relays. Interested in the power and grounding locations on all.

Thanks,
Bryan

Bill, You will have to shoot me some pics or a PM when you get the car done. I know that you have done some similar upgrades and would like to see how everything turned out. Let me know how much more noticeable the power is.
Old 05-04-2008, 05:29 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
OFF THE BOOST PIPE NOW...
 
A930Rocket's Avatar
 
Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
Posts: 7,473
Bryan,

Shoot me your email address and I'll send you the diagram.

I would also consider bypassing all the electrical crap in the back and wiring your relays into a inertia switch for the ground. Also, do the Lee Rice electrical upgrade for the relays. Since I didn that, I've had no problems.

Jim
Old 05-04-2008, 06:08 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
My Yellow Overboost Relay

It looks like my relay (at least the rubber that it attaches to is pretty new. You can see in the pic below that there is some shrink tape where it had been added at one point.

Does everyone have this white plastic connector on their yellow relay wiring as well. It looks to be oem, but I'm guessing that since my yellow relay was not mounted into the metal tin (dangling around) that your white plug would be under the metal tin. Lastly, the pins on the relay look to be in great shape. Can this relay fail some times or is it working or not working??

Any thoughts. We are checking all grounds and power supply this evening to see what else could be wrong.

Bryan

Old 05-05-2008, 04:30 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Forgot something

Does a 930 have the DME relay under the seat, ore is this only with normally aspirated vehicles?

Thanks,
Bry
Old 05-05-2008, 04:32 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
OFF THE BOOST PIPE NOW...
 
A930Rocket's Avatar
 
Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
Posts: 7,473
The yellow relay can go bad with loose connections inside. Also, the external pins can crack or the connections can go bad. Clean them all, spread them out for good contact. Use a little Dielectric grease as well on all connections. Double check all the wires on the set up, since it's been spliced.

I wonder why the female part was replaced? Why is it not installed in the correct position?

Don't forget, you can bypass all this non-sense and fix your problem once and for all by adding a inertia switch to the relays up front on the ground circuit to them.

Quote:
Originally Posted by x98boardwell View Post
It looks like my relay (at least the rubber that it attaches to is pretty new. You can see in the pic below that there is some shrink tape where it had been added at one point.

Does everyone have this white plastic connector on their yellow relay wiring as well. It looks to be oem, but I'm guessing that since my yellow relay was not mounted into the metal tin (dangling around) that your white plug would be under the metal tin. Lastly, the pins on the relay look to be in great shape. Can this relay fail some times or is it working or not working??

Any thoughts. We are checking all grounds and power supply this evening to see what else could be wrong.

Bryan

Old 05-05-2008, 05:36 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
mark '87 930's Avatar
 
Join Date: Feb 2006
Location: Toronto, Ontario
Posts: 727
Garage
have you checked your fuel pump wiring. The wiring in this car is not entirely 'adequate' and the heat build up from teh current drawn by those two fuel pumps is significant over time. the wires will then start to corrode and provide resistance/no connectivity. Have you checked your connections at your fuel pumps?

I have a diagram if you need one.
__________________
1987 930
1956 Chevy 3100
2009 Subaru Forester
2003 KX250 X2(I like my toys!!)
Old 05-05-2008, 05:48 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Fuel Pumps

Mark, I will check that. However, they cut off at the same time which would mean that it is either a Over-boost switch, Ground, or power issue.

I had bigger problems tonight. I will explain below.

1) My friend (cl8ton) and I attempted to tackle this tonight. We had a volt meter up and attempted to re-enact what ever happened before with no success.

In the wiring schematic, fuse #8 (on the fuse block of 1-10) was labeled as the connections for the fuel pump relays (for pin 86) and we founds that the fuse was faulty. The problem was that in the shop manual the fuse is for back-up lights, emergency flasher relay and rear turn signal lights.

Can someone explain why the two documents are off? We still have not found the culprit but were digging in further.

Any help is appreciated.

Bryan
Old 05-05-2008, 08:58 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
Forgot something

Fuse number 8 is in fact for those lights listed above... not for the fuel pump relay.

Does anyone know which fuses (besides the relay) are involved with the fuel pumps besides fuse #3 (in the block of 1-10)?

Thanks,
Bryan
Old 05-05-2008, 09:01 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
A930Rocket

Can you also explain what an inertia switch is??

If I had to guess, if you get in an accident and the car stops abruptly, the switch will sense G's or inertia and shut off the the fuel. Am I right.

Also, what does it replace, how do you buy it, and would this effect my ability to pass emissions in any way (I'm guesssing no)?

Thanks again,
Bryan
Old 05-05-2008, 09:05 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
OFF THE BOOST PIPE NOW...
 
A930Rocket's Avatar
 
Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
Posts: 7,473
You got it right. It's just a switch that upon impact cuts the power or ground in this case to the fuel pumps. With no fuel, the engine stops running, which is what the blue switch does on the back of the flapper housing. It won't do anything to emissions and evrything can be left in place.

Quote:
Originally Posted by x98boardwell View Post
Can you also explain what an inertia switch is??

If I had to guess, if you get in an accident and the car stops abruptly, the switch will sense G's or inertia and shut off the the fuel. Am I right.

Also, what does it replace, how do you buy it, and would this effect my ability to pass emissions in any way (I'm guesssing no)?

Thanks again,
Bryan
Old 05-06-2008, 10:27 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
 
OFF THE BOOST PIPE NOW...
 
A930Rocket's Avatar
 
Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
Posts: 7,473
Should be just one fuse.

Quote:
Originally Posted by x98boardwell View Post
Fuse number 8 is in fact for those lights listed above... not for the fuel pump relay.

Does anyone know which fuses (besides the relay) are involved with the fuel pumps besides fuse #3 (in the block of 1-10)?

Thanks,
Bryan
Old 05-06-2008, 10:40 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #19 (permalink)
After the next project
 
x98boardwell's Avatar
 
Join Date: Sep 2006
Location: Central Valley, CA
Posts: 1,522
Garage
wiring diagram

OK,

This is what I am show on my wiring diagram. If you chase the .5 BL (.5mm and Blue) wire from fuel pump number II you will see that the wire comes off pin 86 (this also bridges and supplies pin 86 on fuel pump I) and travels along the red arrows and ends up in the fuse box in slot #8.

Why is this happening and on the diagram above it is for reverse lights and hazard lights.

Can someone please help with this one?

Thanks,
Bryan

Old 05-06-2008, 12:18 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 01:45 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.