Fuel Pump won't run

[don hopkins]

I am starting to restore a 914 I bought on eBay. I the car cranks but won't start. I have replaced the fuel tank b/c the old one had black tar at the bottom. I replaced the fuel pump b/c I assumed it was probably in the same condition. But now that I have the new tank and pump in the pump does not work. I don't seem to be getting current to the pump wires. I went the the relay board and checked the relay as a possible cause by switching fuel pump relay with one of the other relays. I guess my next move would be to inspect the path of the positive lead back to the engine to see if it is worn anywhere. Anybody have any ideas of possible causes?

[silver2.0]

check the blue fuse on your relay board, and it's connection. Did you try and test the pump before replacement?

[don hopkins]

The blue fuse looks OK. I also tried removing the fuse and replacing with a wire. Could it be a bad ground connection?

[silver2.0]

It's possible. You need to get out the volt meter, and find out if you have juice down at the connection to the fuel pump. Here this will probably help you. http://members.rennlist.com/pbanders/FPChecklist_frame.htm
Mr. Brad Anders gets the "props" for this link.

[John Rogers]

You did not say what type of induction system the car has? If it is D-Jet then the pump should run for a second or so and then stop and then run when starting the engine and it is running. If carbs, many times the pump is wired the same and will act the same. If you checked the fuse and it is okay then try jumper pins 30 - 87 on the fuel pump relay and the pump should run when the key is on. If it does not run, then test the voltage at the pump with a meter and also the ground as on a stock pump the hot (+12v) and ground are on the same connector. If the pump was relocated to the front, many times the connector can be corroded and cause voltage to drop to 9 or 10 volts and the pump will not usually run with voltage that low. Good luck

[Dave at Pelican Parts]

Yup, Silver 2.0's link is specifically for the D-jetronic (stock 1.7, 2.0) system. The 1.8 (stock 1.8) uses a different control system, and carb'ed conversions use whatever the converter felt like hooking up...

--DD

[don hopkins]

Well that helps b/c I have been turning the key one click to the right and then testing the circuit. If it does not stay on until the starter kicks in I have been misled. Since I plan to install Weber 44 IDF carbs maybe I shoud set up a separate circuit so the pump can build pressure for a couple of seconds before I try to start it. When I start my 911SC I turn the key and let the pump run until I get around 3 psi and then start.

[silver2.0]

You don't want to use the stock pump for carbs imho. WAY too much pressure. So now is the time to decide what you want I guess.

[John Rogers]

As noted, the stock pump is way to much pressure, carbs need 3 to 4 PSI only. If you are going to convert to carbs now, then all you need is a switched 12 volt supply to the pump. You do not need the normal start circuit with fuel pump relay at all. If you are going to try to get the engine running with the FI system, then you need to do the troubleshooting as noted. As you just noted, with the key one position to the on position, the pump will not normally run, even if all is right. Good luck

[don hopkins]

I have a low pressure pump. I plan to install it on the firewall in the engine compartment by soldering a wire from one of the relay board's unused pins. I will use an in-line fuse and will eliminate the return fuel line and seal the 2nd outlet in the tank. Does it matter where I mount the pump in the engine compartment?

don hopkins

[John Rogers]

I'd recommend mounting the pump up front under the fuel tank. You can run a switched 12 volt line from the fuse panel through the dash to the pump. There are several extra unused lugs that can be used. Several advantages are there is no heat there, less distance to have the pump suck the fuel since the pumps are better pushers than suckers and you are going to have to get under there anyways to block off the lines you don't need. This might also be a good time to replace the plastic fuel line in the tunnel with a new piece of hard line such as 3/8 inch steel brake line. If you decide to mount it in the engine compt, mount it above the engine sheetmetal to keep it away from the heat. Good luck

[don hopkins]

Ok. I have found the problem (I think). Its at the board in the engine compartment. The pump runs off a wire that is red and black. If I pull the wire out and touch it to a live wire the pump starts to run. What should I do now?
The pump wire connects to the front most left pin on the series of pins closest to the passenger compartment. If I touch it to the wire that is in the same row but the next to the last on the right and have the key on the pump starts to run. I assume this wire is connected directly to the battery. But, strangely enough, at the same time the windshield wipers started to work. Can anyone tell me what each pin is connected to?

don hopkins
______________

[silver2.0]

WOW. sounds like you might have the insulation worn off of some wires. If I remember correctly the windsheild wipers are in no way associated with the realy board, or anything to do with the fuel pump. You probably have some bad wires.

[don hopkins]

Does anybody have a diagram showing what each pin is for?

don hopkins

[silver2.0]

if you have one of the djet years click on the link I posted earlier. It's all there, and accurate.

[don hopkins]

I checked it. It gives a diagram but it does not indicate what each of the pins is for. It shows them but does not give a legend which corresponds with the numbers in the diagram.

don hopkins

[John Rogers]

Here's how I deciphered the two relay board connections, front one is 14 pin and rear is 12 pin. Check and print (color printer) the pelican diagram for the relay board, although it says 1973 is is the same for our 73 and 74 914s. Then look at the diagram for a 1974 914 that shows the tach connection (black and purple wire) and note in the middle that it has two notations: #1 says T-7-14 and the other says T-5-12. If you notice the T-7-14 corresponds to the #7 pin on the front (14 pin) connector. The other, T-5-12 means pin #5 on the rear (12 pin) connector. Now, take the rest of the electrical diagram and find the other wires that show a T-x-14 and T-x-12 notation in them and they will correspond to the wire colors on the relay board picture. To verify this, you can unplu the rear (12 pin) connector and pop off the top of it and see the black/purple wire is in fact connected to pin #5. DO THIS CAREFULLY since these connectors are old and delicate. Good luck

[don hopkins]

OK. I was up til 2am last nite studying wiring diagrams. I think I identified some wires: #13-red and black: fuel pump; #14-red:battery; #11-green: heater fan;#12-red:battery;#9-green and white:heater switch;#10-brown: ground: #8-black: fuse box; #4-yellow: steering column switch. When I touched 13 to 4 the pump ran.

don hopkins (i am now half blind)

[John Rogers]

Isn't this fun......Just think, at least we can do this instead of having a mechanic need a computer to tell you what is wrong!!

[silver2.0]

Don, your lucky to have such a knowledgeable mechanic helping you. (john R). I will pm you with some good info.