1987 3.2L - fuel pump question

[baloo]

My 911 -3.2L has sat for about 6-8 months now since it last run. I had pulled the gas tank and dipped and RedCoated it. Did nothing else to it.

Now, when I go to start it since the tank fix, it just cranks but does not catch. Not even a pop or attempt. Cranks very strong, but nuthin'.

I checked the fuel pump while the key was turned on, and there is no whirring of the fuel pump. I checked the voltage at the fuel pump connections -- no juice coming in.

Should I be getting juice to the pump when the key is in the ON position, or does it only get juice when it is running?

Any suggestions before I start a universal check of all systems?
Thanks.

[DRACO A5OG]

Place a 12volt source on it even a 9 volt could turn the motor or jumper the DME relay, do search there are a few pics on that.

or Safely jack her up with stands and have some one start her and see if you feel it vibrate.

If after the initial attempts to start and you do not smell fuel, then it is definitely a fuel related issue

[DRACO A5OG]

You can also try some starter fluid in the AFM intake, but use sparingly.

[baloo]

Originally Posted by DRACO A5OG

Place a 12volt source on it even a 9 volt could turn the motor or jumper the DME relay, do search there are a few pics on that.

or Safely jack her up with stands and have some one start her and see if you feel it vibrate.

If after the initial attempts to start and you do not smell fuel, then it is definitely a fuel related issue

.......You can also try some starter fluid in the AFM intake, but use sparingly.

Draco,
1) I had the wife start it while I was under the car --- no vibration from the fuel pump.
2) I removed the air filter and sprayed ether into the intake. It started right up and ran for about 5 seconds. Repeated it, and again, it ran short time.

So I guess I'm down to checking the relays. HOWEVER, which relay is it?? On my fuse/relay chart on the front fuse box, there are 6 relays, but none of them are labeled as being fuel pump!? (they're cruise control, aux electric fan, etc, but no "fuel pump")
Where is the FP relay?

[Justin@Athens]

Originally Posted by baloo

Draco,
1) I had the wife start it while I was under the car --- no vibration from the fuel pump.
2) I removed the air filter and sprayed ether into the intake. It started right up and ran for about 5 seconds. Repeated it, and again, it ran short time.

So I guess I'm down to checking the relays. HOWEVER, which relay is it?? On my fuse/relay chart on the front fuse box, there are 6 relays, but none of them are labeled as being fuel pump!? (they're cruise control, aux electric fan, etc, but no "fuel pump")
Where is the FP relay?

Check fuse #3. No relay, other than DME relay located under driver's side seat.

[baloo]

Removed Fuses #3 and 6(?) appear good. Will dig up some new ones and replace them to see if any difference.
However, the car was running fine when I parked it 6 or so months ago -- so this is something new that popped up. I never touched the fuel pump or connections.

[Justin@Athens]

Check for power at fuse 3 with voltmeter with ignition turned to ACC. If no power, most likely DME relay stuck closed. If power present, most likely failed fuel pump.

[cabmandone]

It's early so forgive me if I missed you writing it, but did you jumper the pump to make sure it's working? If you did, wouldn't that indicate that your dme relay isn't telling the pump to kick in? I believe (if I'm not mistaken) the DME relay tells the pump to go.

BTW, my bet is on the DME relay under the seat.

[cabmandone]

PM me your email address and I'll forward the fuel pump checkout procedure along with some schematics. I can't post here because it's in PDF form and probably breaking a copyright law or something.

[KFC911]

Originally Posted by cabmando

....I believe (if I'm not mistaken) the DME relay tells the pump to go.

BTW, my bet is on the DME relay under the seat.

EVERYONE needs a spare DME/FP relay (they're combined and under the seat) for these cars...it's just a matter of "when" . First thing I'd eliminate as a potential cause...

[E Sully]

The DME relay under the seat also controls the fuel pump, through 25A fuse #3. Fuel pump only runs when engine is cranking or running. You can test the fuel pump by installing a jumper from 30 to 87b.
You state that you had the tank dipped and red coated. Was this just the exterior, or did you also internally coat the tank? If you internally coated the tank you may have blocked the internal lines. Later tanks should never use an internal sealant.

[cabmandone]

Originally Posted by E Sully

The DME relay under the seat also controls the fuel pump, through 25A fuse #3. Fuel pump only runs when engine is cranking or running. You can test the fuel pump by installing a jumper from 30 to 87b.

Great advice. I couldn't remember which terminals it was on the DME relay block.

From Bentley;
"The DME main fuel pump relay contains two relays within a single housing. One relay is the DME main relay and the other is the fuel pump relay"

[baloo]

Originally Posted by cabmando

Great advice. I couldn't remember which terminals it was on the DME relay block.

From Bentley;
"The DME main fuel pump relay contains two relays within a single housing. One relay is the DME main relay and the other is the fuel pump relay"

Sully/Cab,
Will check the relay right now -- if I can figure it out. I dug up old Pelican threads on the testing, and should be able to figure out the terminals to jump.

Yes, I coated the inside -- the tank was leaking like a clogged sieve (very slow drops would form at multiple locations, over several days. When I washed it out with acid, the holes popped out. I sealed it with RedCote like I have done with many other gas tanks (not POrsche though). There are no leaks anymore, despite now having sat with gas in it for a few weeks.
While I did run a long bore brush up the inlets/outlets to ensure that they were not clogged, it's no guarantee there isn't a flap, I suppose.
However, I'm thinking that the pump would at least have been running.

I'm going to check the relay.

[E Sully]

This thread shows internals and why coating of CIS and Motronic fuel tanks can have problems.
CIS Gas Tank

[baloo]

Originally Posted by E Sully

This thread shows internals and why coating of CIS and Motronic fuel tanks can have problems.
CIS Gas Tank

Very good! Thanks. Wish I had seen it before. However, still testing if the fuel pump is working.

So far, yes, there is power to Fuse #3.
I pulled the relay under the driver's seat, and there are two terminals marked 87b.
I jumped across #30 and one of the 87b's. nothing.
I then jumped across #30 and the other 87b. Again, nothing.
Did I do this correctly? Why are there two 87b's?
Should I be jumping across both 87b's as well as #30?

I guess my next step is to go directly to the fuel pump with current and see if it works.

Any other ideas?

[cabmandone]

Originally Posted by baloo

Very good! Thanks. Wish I had seen it before. However, still testing if the fuel pump is working.

So far, yes, there is power to Fuse #3.
I pulled the relay under the driver's seat, and there are two terminals marked 87b.
I jumped across #30 and one of the 87b's. nothing.
I then jumped across #30 and the other 87b. Again, nothing.
Did I do this correctly? Why are there two 87b's?
Should I be jumping across both 87b's as well as #30?

I guess my next step is to go directly to the fuel pump with current and see if it works.

Any other ideas?

Email sent with diagnostic info. Also email with pic of DME relay showing pin 30 and 87b. There is only one 87b terminal.

[baloo]

Cab,
Yah, I was reading the relay wrong (needed to use a magnifying glass -- then I saw there was only one 87b).
I have juice to #30; I have juice to #86 with key on; I have ground to whatever number terminal is supposed to be the ground (can't remember). Fuse #3 has juice on both sides of the fuse, so fuse is good too.

Nick -- big thanks for the pdf files and pics.
Tomorrow, will try to re-jump #30 and 87b terminals of the relay socket. I tried it once and got under the car, but the fuel pump was not vibrating. However, I need to try it one more time to make sure the contacts were good.

If that fails, I'll get under and hook leads directly to the fuel pump.
If no-go, I'll pull the pump and check for clogged lines and bench test the pump.

I'm thinking that I better pull out the screen filter in the bottom of the tank to see if it is clogged.

Thanks to all for the advice, and I'll report back with what I find out next.

[cabmandone]

Originally Posted by baloo

Cab,
Yah, I was reading the relay wrong (needed to use a magnifying glass -- then I saw there was only one 87b).
I have juice to #30; I have juice to #86 with key on; I have ground to whatever number terminal is supposed to be the ground (can't remember). Fuse #3 has juice on both sides of the fuse, so fuse is good too.

Nick -- big thanks for the pdf files and pics.
Tomorrow, will try to re-jump #30 and 87b terminals of the relay socket. I tried it once and got under the car, but the fuel pump was not vibrating. However, I need to try it one more time to make sure the contacts were good.

If that fails, I'll get under and hook leads directly to the fuel pump.
If no-go, I'll pull the pump and check for clogged lines and bench test the pump.

I'm thinking that I better pull out the screen filter in the bottom of the tank to see if it is clogged.

Thanks to all for the advice, and I'll report back with what I find out next.

No problem. Let me know what you find when you jumper the terminals. Your pump should run with the Key on Ignition off and the terminals jumped together if I recall correctly.

[baloo]

Latest on testing...
I jumped terminals 30 and 87b, and nothing.
HOWEVER, the fuel pump got very hot!
So, I'm wondering if it got clogged with the RedCote tank sealant.

I will do the following:
Remove the tank filter and see if it is clogged;
Remove the fuel pump and check for clogging, as well as bench test.
When I contacted RedCote regarding using their stuff, they said not to worry, because the coating would not stick to plastic... so there will be a certain amount of liability here if I find a floating redcoat flap.

Will update in a few days when I find out more.

[scarceller]

Disconnect the wires from the pump and put a volt meter or test light across the wires. Then crank the starter and while cranking you should have 12vdc at those wires. The pump only gets power while cranking, then once engine starts the DME keeps the power to the pump.

You can also force the pump on even with the key out of the ignition. To do that test simply jumper the fuel pump fuse to the adjacent fuse with a jumper or a coin. You jumper Fuse #3 (fuel pump fuse) to the adjacent Fuse #2 (central locking fuse). When you jumper these 2 together the pump will get 12vdc. This works because fuse #2 always has power even if the key is not in the ignition.