82 SC died while driving, narrowed down to fuel pump I believe

[QueWhy]

Solved. Ordered a new fuel pump from pelican, followed the instructions in 101 projects and it fired right up!


My 1982 3.0 died on the way home after a fairly long drive. It just quit, the lights and electronics worked fine and it would crank but no start. I had it towed the last mile home and tried to diagnose the issue.

I first opened up the fuse box in the trunk and none of them were blown but the wire going into the fuel pump fuse was fried and the connection for the fuse to the block was corroded and green.



I cut the wire back, cleaned up the block and installed a new fuse. NO START. I then removed the air box and push up on the plunger in to activate the CIS with the key to ON. I didn't hear anything that sounded like injectors firing or the fuel pump from up front. I then tried removing the red fuel pump relay and jumping terminal 87a and 30. All I can hear is a click from under the car, no sound of the pump running.

What is the next step? Test the terminals of the fuel pump itself to make sure it is getting power?

If the pump is getting power and not running is it safe to assume it is the culprit. Would a failing pump cause the fried wire and corroded fuse or is that a separate electrical issue? I hate to get a new pump then fry it because of a different issue.

There is a wide disparity in cost between fuel pumps available from our host ~$100-$450 without many reviews. Is a $100 Dansk unit asking for trouble?

Any help is greatly appreciated. I'm eager to start my SSI project but I need to get the car running first.

[Avanti]

If the pump is not getting power then I would say its the cause. The corrosion on the wire looks pretty old. Quite possible the resistance at that connection over time caused the pump to fail.

I have an off-brand pump and have not had any problems. Never used the Dansk pump but I am happy with the products Dansk offers.

[QueWhy]

Originally Posted by Avanti

If the pump is not getting power then I would say its the cause. The corrosion on the wire looks pretty old. Quite possible the resistance at that connection over time caused the pump to fail.

I have an off-brand pump and have not had any problems. Never used the Dansk pump but I am happy with the products Dansk offers.

I haven't tested for power at the pump yet. I've got the car wedged in the garage and getting the front up in the air is going to take some maneuvering. I'll try to make time for it tonight or maybe tomorrow morning.

[autojack]

I'm not sure if the SC has a DME relay like my 88 does, but if so you can test the fuel pump by jumpering two pins on the DME relay socket. This puts 12v directly to the pump with the engine off. If you hear nothing, the pump or wiring is bad. When this happened to me, giving the pump a whack when power was applied caused it to run for a second and then stop again. That was the smoking gun I needed. The details of this are in the Bentley manual.

[tirwin]

Apparently, this is contagious. I'm fighting with my own fuel pump problem on my '83 tonight.

When you jump 30 to 87a you should hear the fuel pump running. If it's not running then that's probably a bad fuel pump.

Something you can try is to disconnect the rev limiter. It is behind the fuel gauge. The east way to reach it is through the trunk. Reach in to the right and you'll feel a box with a 6-pin wire connecting from the bottom. Wiggle the connector down and unplug it. That should eliminate the rev limiter while troubleshooting.

You probably know already, but the fuel pump is a 2-stage deal. There is the initial engine crank and then the FP relay triggers the normal operation of the fuel pump.

If you disconnect the air pressure plate sensor on the back of the FD, it will allow the fuel pump to run when the key is turned to the last position before starting. You should hear it running before you turn the key to start the car.

Also check the FP ground.

[tirwin]

Originally Posted by autojack

I'm not sure if the SC has a DME relay like my 88 does, but if so you can test the fuel pump by jumpering two pins on the DME relay socket. This puts 12v directly to the pump with the engine off. If you hear nothing, the pump or wiring is bad. When this happened to me, giving the pump a whack when power was applied caused it to run for a second and then stop again. That was the smoking gun I needed. The details of this are in the Bentley manual.

SC doesn't have a DME.

[QueWhy]

I got the front of the car in the air and busted out my multimeter. With the fuel pump relay in place and the key to "ON"(CDI buzzing away) I got 0.06 volts across the terminals. With a jump wire in place of the relay it was right around 9 volts. No action from the fuel pump in either instance.

[QueWhy]

With the information given is it safe to assume the pump is the culprit and order a new one?

[3rd_gear_Ted]

There is a OEM mesh screen filter in the tank.
The -044- style pump used is a diaphragm pump and will NOT tolerate contamination.
Weak link in chain.
Suggest install of in line auxiliary filter "while your there"

[glewis80SC]

I had this happen twice both times it was a bad coil the newer Bosch are junk.

[QueWhy]

Originally Posted by 3rd_gear_Ted

There is a OEM mesh screen filter in the tank.
The -044- style pump used is a diaphragm pump and will NOT tolerate contamination.
Weak link in chain.
Suggest install of in line auxiliary filter "while your there"

I've wondered about sediment in the tank. This may be a good opportunity to drain it and check it out. I'll look into adding an auxiliary filter too.

Originally Posted by glewis80SC

I had this happen twice both times it was a bad coil the newer Bosch are junk.

If the coil is bad how would that keep the fuel pump from running when being jumped at the relay or activated by lifting up on the plunger to get the CIS system started?

I guess I should check for spark but it seemed like the fuel pump not running was the cause of the car dying on the way home and failing to start since.

[Quinlan]

Definitely check the ground. I had mine go and chased things for a while before finding it. Just run a jumper wire from the FP neg to the nearest bare metal or ground location (or right to the battery negative to be absolutely sure), then try lifting the plunger again. It's a quick and free way to rule that out.

[pmax]

Originally Posted by QueWhy

With the information given is it safe to assume the pump is the culprit and order a new one?

Time to crawl under the car and check it out yourself.

https://www.pelicanparts.com/techarticles/911_fuel_pump/911_fuel_pump.htm
https://www.pelicanparts.com/techarticles/Porsche-993/44-FUEL-Fuel_Pump_Check_Valve_Replacement/44-FUEL-Fuel_Pump_Check_Valve_Replacement.htm

[Targalid]

Run two wires with alligator clips from the battery out of the frunk, under the car and test the pump with twelve volts. That eliminates all the intervening uncertainty in the wiring. If the pump does not function when directly jumpered from the battery you have identified a faulty pump.

[imoto]

I had a fuel pump issue with an 81 SC jumped the pins on the relay base no good , checked for power at the pump terminals and had 12 v so I removed the pump , terminals were nice and clean. Once it was out I connected it to my battery charger just to see and it ran so I reinstalled it and it has run since !! That was 2 years ago .

[Bob Kontak]

Check voltage at the fuse block, The metal thingie that holds the fuse. Then check the crusty part of the wire voltage without touching the fuse block.

Long story short, get 12V to the FP before ditching it. 9V may not run it.

If there's 12 at the fuse maybe the relay is getting tired?

[3rd_gear_Ted]

If you had a long term low voltage condition (as maybe indicated by the fried wire)
The relay contacts will pit due to the increased current draw.
Fix the fuse block wire termination and get good mechanical contact to newly tinned wire end
Replace the fuel pump relay
Get another -044- pump from anywhere but Brazil
Drain tank and remove tank filter, then be amazed
Install in line fuel filter with adequate flow rate for 65 PSI
Look real close at the rest of the fuel lines to feel better
Go to Cars and Coffee and tell story during the "did you know part"

[Bob Kontak]

Originally Posted by 3rd_gear_Ted

If you had a long term low voltage condition (as maybe indicated by the fried wire)
The relay contacts will pit due to the increased current draw.
Fix the fuse block wire termination and get good mechanical contact to newly tinned wire end
Replace the fuel pump relay
Get another -044- pump from anywhere but Brazil
Drain tank and remove tank filter, then be amazed
Install in line fuel filter with adequate flow rate for 65 PSI

Nice write up. Thanks.

The pump pushes around 100 psi until stepped down by the fuel distributor to system pressure. Would that impact the through-put capacity needed for the in line filter? Seems it would.

Also, only because I have done this, if not much in the tank you can pull tank filter first and allow tank to drain into a tub. I observed no cooties in my car but I have in an XJ 12. I did repeated tank rinses straining drain gas through an old t-shirt before pouring back through.

For the 911 tank plug I had a big cold chisel that had a shank that fit perfectly. Crescent wrench to loosen. May be a PITA to find the right size allen wrench. Industrial supply house, perhaps?

[Bob Kontak]

I think 12V to the pump is most important.

[Superman]

Voltage when the car is running and the headlights off should be around 13.5+ volts. With the headlights on, less. With the engine off, more like 12.8 with the headlights off. With the engine and headlights off....12.6V+. A battery not reading well in excess of 12V with the engine and headlights off should be replaced.

Clean electrical terminals are essential. There is virtually nothing you can do to your car more important than cleaning and/or wiggling all the electrical terminals. Best practice is to clean with vinegar and coat with Dow Corning 111 or 112.

I have heard of fuel pumps failing. Even while the car is running. The advice those drivers would offer is to just replace the FP. Before being stranded.

So yeah, that is my advice. Replace the FP, clean the terminals and make sure your battery is doing its job. Problem(s) solved.