73 914 won't start

[e065206]

Fuel injected stock 4 cylinder.

Turn ignition key to on, I hear fuel pump run for a fraction of a second. If I "prime" the fuel system by turning key on then off about 10 times, and then turn ignition key all the way to start, the engine does fire and run for a few seconds but then dies.

It seems I can run with the fuel I primed into system, but then no more fuel flows to keep the car running.

I have replaced the spark plugs and coil, even tho I don't suspect them based on these symptoms. I have swapped relays 11 and 12, as well as tried some spare relays, but still no go.

Wondering what to try next. Is there another relay or fuse that causes the fuel pump to run? Or do I need to troubleshoot the computer?

Thanks for the advice.

[TheCabinetmaker]

the pump should run a little more than a second I recall, without the motor turning, the fact that you prime it and she runs is interesting.
their is a pump relay but if you hear the pump, then it is working. it is controlled by the ecu, usually the ecu's are bullet proof unless you short some wires and kill them.

your trigger points appear to work since you say the motor will run after priming with the key several times. (unless it is only running form the cold start fuel , which only operates at very cold temperatures normally) just to be sure, since you did work with the distributor, make sure the little three prong plug at base of the dizzy is correctly plugged in, this is for the trigger points which control the injectors

it is still possible you have an intermittent fuel pump fail, loose wires maybe?

to get the pump to run constantly you can jumper the pumps relay then it will run when ever the key is on,(don't drive around like this, it can be a fire hazard, in event of crash for instance, the pump will keep running till you turn off the key and that could spill a lot of fuel)
the relay is on the relay plate, in engine bay behind the drivers seat (get the Haynes manual to help you with the car, it is very useful and cheap to buy) there are four relays (or three, if you dont have the optional rear window heater, although some car without the heater do have the heater relay installed)
the Haynes book shows this info, assuming you don't have the book yet, the relays are as follows
from fire wall behind driver seat back, the one nearest firewall is the window heater, next towards rear of car is main ecu relay, then next is fuel pump relay, and next is cabin heater fan relay.
you can short the pump relay as follows, by shorting with a wire the sockets 30 and 87 together. besure you short the correct ones, else there may be damage to the ecu the relay plate is not numbers, but the relays themselves have numbers for their pins on the relay body, so transfer them number to the socket and you can short it out.
with the pump relay socket shorted as above, the pump should always run when the key is on. (also note that all four relays are interchangeable with each other)

see if the car runs fine now.

if note there are other things to check. you already addressed the ignition system and set the timing correctly right?

could be the head temp sensor has failed, this can cause an extremely lean mixture, so lean the cold motor will not run when cold. use an ohm meter to test this, disconnect the pig tail wire from the sendor and with an ohm meter measure the resistance on the head temp sendor pigtail to ground. do not connect the ohm meter to the wire going into the harness, only to the head temp sendor pigtail after the pigtail is disconnected form the harness. beusre to wiggle the pigtail wire a good eal during this test as often the pigtail wire is at fault, shorted or broken at the base of the sendor
with a cold motor you should read about 2k ohms, a hot motor should be near 100 ohms or so (I don't have the exact numbers in front of me, but these are close enough to see if it is more or less right) besure again to wiggle the pigtail looking for intermittent shorts or opens.
see if this helps you.

PS What do you mean by relays 11 and 12?

[e065206]

Originally Posted by TheCabinetmaker

your trigger points appear to work since you say the motor will run after priming with the key several times. (unless it is only running form the cold start fuel , which only operates at very cold temperatures normally) just to be sure, since you did work with the distributor, make sure the little three prong plug at base of the dizzy is correctly plugged in, this is for the trigger points which control the injectors

I will check this tonight.

Originally Posted by TheCabinetmaker

it is still possible you have an intermittent fuel pump fail, loose wires maybe?

I don't believe so. Thoroughly tested the fuel pump last eve to ensure it was pumping fuel when we turn key to on.

Originally Posted by TheCabinetmaker

to get the pump to run constantly you can jumper the pumps relay then it will run when ever the key is on,(don't drive around like this, it can be a fire hazard, in event of crash for instance, the pump will keep running till you turn off the key and that could spill a lot of fuel)
the relay is on the relay plate, in engine bay behind the drivers seat (get the Haynes manual to help you with the car, it is very useful and cheap to buy) there are four relays (or three, if you dont have the optional rear window heater, although some car without the heater do have the heater relay installed)
the Haynes book shows this info, assuming you don't have the book yet, the relays are as follows
from fire wall behind driver seat back, the one nearest firewall is the window heater, next towards rear of car is main ecu relay, then next is fuel pump relay, and next is cabin heater fan relay.
you can short the pump relay as follows, by shorting with a wire the sockets 30 and 87 together. besure you short the correct ones, else there may be damage to the ecu the relay plate is not numbers, but the relays themselves have numbers for their pins on the relay body, so transfer them number to the socket and you can short it out.
with the pump relay socket shorted as above, the pump should always run when the key is on. (also note that all four relays are interchangeable with each other)

see if the car runs fine now.

Will try the jumper asap. May not get back to it till Friday. I did swap out the relays you mention on the panel. I referred to relays 11 and 12 because that is how they were labeled in the photo in my Haynes manual. There are currently locations for 4 relays, but I am only using the 2 in the middle for fuel system.

Originally Posted by TheCabinetmaker

if not there are other things to check. you already addressed the ignition system and set the timing correctly right?

yes, timing is set properly - I checked.

Originally Posted by TheCabinetmaker

could be the head temp sensor has failed, this can cause an extremely lean mixture, so lean the cold motor will not run when cold. use an ohm meter to test this, disconnect the pig tail wire from the sendor and with an ohm meter measure the resistance on the head temp sendor pigtail to ground. do not connect the ohm meter to the wire going into the harness, only to the head temp sendor pigtail after the pigtail is disconnected form the harness. beusre to wiggle the pigtail wire a good eal during this test as often the pigtail wire is at fault, shorted or broken at the base of the sendor
with a cold motor you should read about 2k ohms, a hot motor should be near 100 ohms or so (I don't have the exact numbers in front of me, but these are close enough to see if it is more or less right) besure again to wiggle the pigtail looking for intermittent shorts or opens.
see if this helps you.

Thank you very much. Will give this a shot if other tests don't work. I really appreciate the info.

Originally Posted by TheCabinetmaker

PS What do you mean by relays 11 and 12?

These are the 2 middle relays on the board behind the driver seat. In the photo in my Haynes manual, they were labeled 11 and 12 and then defined below the picture.

[TheCabinetmaker]

I have several editions of the Haynes book, all call out the relay numbers the same, for instance my 1989 edition, page 181 shows the relay plate for 1973 models, from front of car to back they are numbered 52, 74, 75, 55. This is in the schematic section

the numbers your refer to on page 128 are for the key that goes with the photograph, this is not VW's electrical designation., rather it is only for this photograph, the schematic on page 181 is the real VW designation. (not sure, but this might even be a DIN designation)
If you refer to these numbers, (52, 74,75, and 55) it will make more sense to most folks.
No harm, no foul.

[e065206]

Originally Posted by TheCabinetmaker

the numbers your refer to on page 128 are for the key that goes with the photograph, this is not VW's electrical designation., rather it is only for this photograph

Yes! Thats exactly the page I was looking at. You're good...!

Thanks again.
-Vinny

[e065206]

Originally Posted by TheCabinetmaker

just to be sure, since you did work with the distributor, make sure the little three prong plug at base of the dizzy is correctly plugged in, this is for the trigger points which control the injectors

Tested this tonight. unplugged and replugged in a couple times to be sure. Did not solve the problem.

Originally Posted by TheCabinetmaker

you can short the pump relay as follows, by shorting with a wire the sockets 30 and 87 together.

When I go to short these 2, do I put the jumper wire between the sockets and then reinsert the relay? Or instead, leave the relay out?

Originally Posted by TheCabinetmaker

could be the head temp sensor has failed, this can cause an extremely lean mixture, so lean the cold motor will not run when cold.

Where do I find this sensor? I know it is tempting to say "It is in the head."

Thanks again.

[TheCabinetmaker]

leave the relay out, simply put a jumper in the socket, make sure you get the right two sockets, check twice before you commit. once jumpered, see if the pump runs constantly, it should.

the head temp sendor is on the passenger side head, on top. You can see it just forward of the #3 spark plug hole in the cooling tin over the head. the pigtail wire sticks out of a hole simular to the spark plug hole, only a little smaller diameter, the hole may be kind of obscured by the intake manifold pipe. there will be a single wire coming out of the cooling tin, and several inches away will be a connector, which hooks the pigtail to the main harness.
what ever you do, only hook the ohm meter to the sendors pigtail AFTER it is pulled off the main harness. Do NOT hook up the ohm meter to the main harness, only hook up ohm meter to the separated pigtail. measure the ohms between the pig tail and ground. since you cant get the engine warm, you will only be concerned with the cold temperature reading. also besure to wiggle the pigtail wire a good deal whilest ohming it out to make sure there is no intermittent short or open to ground in the pigtail. often the wire fails at the sendor, and either the conducters break, causing an intermittent open, or the insulation tears, causing an intermittent short. wiggling the pigtail will help determine if the wire has failed or not.

[e065206]

Just tried jumping sockets 30 and 87. When I jump, the fuel pump comes on immediately - even with the key off. Car will not start.

I was expecting pump to only come on with key. Is it possible that it is not 30 and 87 that need to be jumped?

Measured ohms on head sensor. Got 2750. Sound like that is correct.

[Dave at Pelican Parts]

You have other problems. It seems likely that the FI isn't getting powered.

Have you looked through Brad's '70 914 2.0L ? He has some flow-charts (that seem to be a bit finicky about how they show up) that can help.

--DD

[e065206]

Originally Posted by Dave at Pelican Parts

You have other problems. It seems likely that the FI isn't getting powered.

Have you looked through Brad's '70 914 2.0L ? He has some flow-charts (that seem to be a bit finicky about how they show up) that can help.

--DD

Is Brad on this board? If so, what is his username? As he is local to me, I'd like to contact him directly to see if he can help. I don't want to spend countless hours troubleshooting if not necessary. I've always been happy with the FI performance, but would rather convert to carbs than spend all my time tracking down the smallest gremlin.

Thanks.

-Vinny

[Dave at Pelican Parts]

I don't think he is on here--or if he is, it isn't much. You may be able to contact him through the webpage there.


--DD