fuel pump doesnt prime when ignition is turned on

[MattDon]

thanks wayne, but ive got a CAS i guess your right it might be easier to swap the old HES to avoid the wiring work, and if that doesnt work i could swap the CAS's. Just wish i could workout whats going on with the fuel pump. I ran it for a few seconds and got the engine to fire up and run for several seconds. (thats a start atleast)

[wayne]

update. direct 12v to pump does work, so im back to being confussed, could it be the inertia switch or something between that and the A3 fuse? im trying to work out where the voltage drop comes from someone did say 5v is normal at terminal 3 of the fuel relay, what drops that after A3 fuse? and why am i showing 1.5-2v or is that down to my flatish battery? and if thats normal whats going wrong? ive tried a different relay with no luck.

I have a few spares that you are welcome to borrow, inertia switch etc

I'm in no way a car mechanic or vouch to know anything about them.... but if you suspect it may be the pump and have a spare one.... change it!! at least you will narrow down your troubleshooting..... working and having useable outupt can be 2 different things....... Just a thought.....

I thought mine was fine untill I replaced it..... These pumps are known to fail..... P.s. If you have 12 V to pump and no output....... ?? would this not narrow it down. Sorry for my lack of knowladge.

[DeeAitch]

update. direct 12v to pump does work, so im back to being confussed, could it be the inertia switch or something between that and the A3 fuse? im trying to work out where the voltage drop comes from someone did say 5v is normal at terminal 3 of the fuel relay, what drops that after A3 fuse? and why am i showing 1.5-2v or is that down to my flatish battery? and if thats normal whats going wrong? ive tried a different relay with no luck.

I think terminal 3 of the relay should get 12v, terminal 1 probably 5v but only for the first few secs or when the engine is running. You should also be seeing 12v on one side of the inertia switch. Not sure if the terminals are marked but it is the Purple wire. White / Purple will also show 12v if it is set correctly.

[MattDon]

yeh the terminals are marked, terminal 1 comes from the ECM fuel pump relay driver and shows 11v for two seconds then 0v after, terminal 2 is the earth, terminal 3 comes from fuse A3 to the inertia switch into the relay and is constantly showing 1.5-2v and terminal 5 goes to the fuel pump and the ECM fuel pump signal, ive not managed to get a reading from 5 as it an out and i cant get a connection when the relsy is plugged in but i checked at the pump and its the same as terminal 3.

So it looks like i need to find out why ive got 11v at the fuse but 1.5-2v after the inertia switch.

[DeeAitch]

yeh the terminals are marked, terminal 1 comes from the ECM fuel pump relay driver and shows 11v for two seconds then 0v after, terminal 2 is the earth, terminal 3 comes from fuse A3 to the inertia switch into the relay and is constantly showing 1.5-2v and terminal 5 goes to the fuel pump and the ECM fuel pump signal, ive not managed to get a reading from 5 as it an out and i cant get a connection when the relsy is plugged in but i checked at the pump and its the same as terminal 3.

So it looks like i need to find out why ive got 11v at the fuse but 1.5-2v after the inertia switch.

Hi Matt
I'm thinking high resistance at the inertia switch.
" Not sure if the terminals are marked but it is the Purple wire. White / Purple will also show 12v if it is set correctly" refers to the inertia switch.
Might be worth a temporary bypass to see if you then get 12v at the relay terminal 3 - however I'm not sure what effect you would get if the ECM does not get a signal from terminal 5

[MattDon]

i think i managed to bypass it and the ecm didnt like it, the relay stopped clicking and i dont think it would crank. I'll try to check the inertia switch but the connectors are so small i was struggling to get the probes on. It does seem like the most likely candidate, just a shame i dont have a spare to switch over. Are they hard or expensive to get hold of?

[Monty]

Matt,

I should have a spare inertia switch, send me a PM if you want me to post it to you, at least you can rule that out.

[MattDon]

finaly got to try a different inertia switch and it didnt solve the problem, ive forgotten where i was at with this problem, but id love to get it sorted before the baby comes.

open to any further suggestions, but pulled out the internals from my other fuel tank maybe its worth wiring it up to see if it primes.

[MattDon]

so plugging in the guts from another fuel tank didnt work, inertia didnt work, fuses have been checked, this is proving to be a right pain.

[Monty]

Thats weird

Is there a relay?

Has the elan got an immobilizer?

Would it be possible to hook up the fuel pump direct to battery to make sure it runs?

[MattDon]

actualy mate id already tried that so swapping the guts around was a bit of a waste of time, yes there is a relay think that is my next port of call, but it does click after 2 seconds so its doing something.

I found the chart (ekm 4-5) in the manuals for this problem but i cant make any sence of it, it referes to test which arnt mentioned, help!?

cheers

[MattDon]

determinded to crack this today.

tried to date:

Inertia switch
relay
fuel pump
fuse d2
fuse a3

going to check voltages again across various points, earthing points.
the immobiliser is playing on my mind, but it seems to be working fine, but im not sure how to turn it off, its a factory unit.
the ECM is also playing on my mind but if its clicking the relay after 2 seconds it seems to be safe to assume its working ok.

[MattDon]

ok its a wiring issue, ive got 13v at A3 fuse but only 2v at the inertia input, so the big question is where does the wire run and where are the likely problems.... i realy dont want to be chasing a wire through the interior

[Monty]

Have you had the center console out (were the handbrake is)? maybe a wire has got trapped

[MattDon]

pulled out an old loom and chased the wire to see the route it takes and thats not something id like to do on my nice siny S2, would mean pulling parts of the dash out which id rather not risk, so im going to splice in a new wire and griptie it to the old loom where i can and bypass the trickier areas. think i'll just run a wire between the fuse and inertia switch and see if that works, but all my wire cutters and connectors are at work so looks like its not going to be today. If anyone can tell me how best to pull one of the connectors out of the A fuse box it would help, think i'll just put a bullet connector before the intertia switch.

monty, no ive not had the console out, only had the car a year and not used it much in that time. just cant workout where it couldve worn apart from where it goes into the console like you say, might lift it to double check.

[John V6]

Have you an Alarm / Immobiliser fitted ?

Had similar problem and had to replace unit

[ashm]

Sounds like an immobiliser, as this would hook into the circuit serving the fuel pump.

When I got a new TOAD unit installed in my car the electrician pulled out enough old alarm & immobiliser equipment to fill the passenger footwell. He said he was surprised the car even ran at all, as he found parts of three different systems, all still partially wired in but none working properly! Took him hours to repair all the looms back to stock... I wouldn't be surprised if there's some half-installed piece of old immobiliser kit causing trouble with your pump circuit.

Adam

[MattDon]

YEHY ITS THE WIRE, i put a wire between the fuse and inertia switch and everything worked fine. The only immobiliser is the factory unit and it seems to be working fine, the big question now is how do i disconnect the old wire coming out of the fusebox. its some sort of crimp on connector which id also need to source, can take a pic if it helps.

who would have thought it, guess i should try to find the problem but its a tricky job.

[RayD]

... the big question now is how do i disconnect the old wire coming out of the fusebox.

I’m not fully up on where you are with this Matt, but with regard to the fuse box rear wiring … I thought they might have been female spade connectors which have been pushed passed a small plastic one way lug.

If so, it will just be a matter of pushing the lug back to release the connector.

Ray

[MattDon]

thanks ray your pretty much spot on, i think what im after is a metri-pack terminal remover (part # t000t0903) and a metri-pack serie 150 conector, but i might be wrong about the connector, cant find them online so has anyone got any ideas, going to try the motor factors today but there pretty small around here.

pulled the correct wire out of my old loom this morning so just need to swap them over now and put everything back how it was, easy