Hello was wondering if someone can help me my fuel pump isn't priming at all. I have put 12v to the pump it works so then tried it at the fuel module that works also got to relay switch in the drivers side kick panel and the relay isn't clicking I have put 12v to this via a power probe tester it clicks and car starts and runs perfectly. I have removed my aftermarket alarm just as a precaution just in case it was the immobolizer still no prime. I'm not good with electrics so any help will be much appreciated thanks to all in advance.

Well you have done a good job of tracking down the issue to almost the last parts of the circuit and also proven most parts after that point.

 

So the relay is not getting a feed to pull in, the feed for the pump and the relay coil come from the same place,the green fuel pump thermal fuse under the bonnet in the slim black box by the brake master cylinder, it is marked up on the lid. If the thermal fuse is good and power on is coming out ok then there is a break in between, but do check the fuse and swap it with an adjacent one for the seats to be sure.

 

Jeff

Thank you Jeff I'm off work today and the weather is nice thank God so it's happy hunting.

Well today has been another failure in afraid I checked the slim fuse box all fuses are ok and swapped them just in case, I then tested power from battery to the fuses (If that's correct) 12v so it seems from the slim fuse box to the relay is where my problem is. But problem I short my relay out now it doesn't start but when I did it last week it fired straight up so I think I'm making a bad situation worse fiddling with wires. Looking around for a auto elec but nobody wants to touch it lol. Does any of you guys know of a good auto elec around south Yorkshire who is willing to work on these cars? Any help will be appreciated thanks in advance.

To help you trace the fault I've attached the full ECCS diagram (in colour). The fuel pump circuit is on the right. This is a

hi-res image so use "view image" or similar to see in 4167×1760.

 

When you say you removed the alarm/immobilizer what did you do to restore the circuit(s) "cut" by it? Depending on make/model,

immobilizers often include the fuel pump circuit.

 

This is where I start to struggle it's an aftermarket alarm a GT636 I just removed the control box and unplugged the immobaliser. Thanks for the diagram I will have a look through it see if I can understand it haha. I have had search around and found a auto elec who works on on classic cars n kit cars near me so going to give them a ring in morning, I don't want to go tampering with something I don't fully understand really getting past my electrical skill now haha.thanks for help really appreciated will let you know how it turns out.

The alarm can cut power to the fuel pump. Are you sure when you're unplugging the alarm it's not just cutting the circuit completely, as you say it doesn't start now?

The car started last week with the same test today and I haven't changed anything inbetween just done some re tracing footsteps etc but could have easily snagged an old wire or something thats what im hoping anyway.i will have another look at the alarm after work tomorrow it's pretty easy to get too.

The GT 636 includes a two circuit immobiliser. The picture below is a (poor) copy of the fitting instructions in english.

You can see that a fuel pump relay "cut" is shown (circled in red).

 

Interesting thank you for the info guys. Looks like I'm booking another day off to have a good go at it. Also had a chat with an auto elec who works on classic cars so hopefully he might be able to help me and I might learn something lol. Cheers guys much appreciated.

Just so you understand the circuit, the relay coil and supply to the pump via the relay contacts comes from that green fuse as we discussed before, this is a battery feed. The relay is switched via the earth to the coil direct from the engine ecu, if you are not careful you can damage the output from the ecu, if your finding the relay will not pull in now that might be the very issue that may of been caused accidentally.

If you just pull the relay and link the contacts then the fuel pump should run if there is power across those contacts. If not just run a new fused supply, often quicker than hunting a fault down.

Or dear i hope not that auto elec is coming Friday morning so fingers crossed he can sort it. If the ecu has thrown it's toys out of the pram does anyone repair them? Or best place to get a second hand 1?

Ecu's are easy enough to get hold off, if that is the case.

 

Jefg

If the ecu is at fault I can get hold of a blitz ecu is this a decent ecu or a no no.....

I can get hold of a blitz ecu is this a decent ecu or a no no.....

 

If by that you mean an OEM ECU with a Blitz EPROM (and mapping) and Blitz stickers on the box then Blitz maps

are typically pretty agressive and designed for high octane Japanese fuel (100 octane).

I will give that a miss then cheers for the reply bud I will stick to the standard one.

IT'S ALIVE!!! The problem turned out to be corroded connector in the passenger footwell tucked up under the glove box right in the corner the auto elec found it couldn't fault the guy new his stuff on older cars. Anyways I'm back on the road thanks for all your input guys and hopefully be able to make the 300zx meet now

On this subject the way the ECU is wired should each and every ECU output be an earth aside from the power in? As in is everything wired to the same formula as the injectors, permanent live with switched earth.