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spandelly · Joined: 26 May 2012 Posts: 23 Location: Manchester England

Hi folks. Been messing with the car again today trying to figure out why it wont start. I have traced it down to a fuel problem. After much messing with various things including fitting a new air fuel regulator I pulled injector 1 and cranked it over to find no fuel coming through. Tried again with injector 4 and thats not got any juice either. I pulled the feed from the fuel filter and its pumping fine to there. After that it started cranking slow and flattened the battery so I gave up there. I was wondering where to go next. I was thinking of trying to clean out the fuel system but I'm unsure what to use.
I'm thinking of filling a bottle with some cleaning fluid and connecting it to the pump. then stick all 4 injectors in bottles and jump the relay and let it pump through the whole system. Do you think it would work and what cleaner should I use. I tried looking but all the stuff I found runs through with the engine running and mixes with the fuel.
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It could always be worse so don't worry about it and get the spanners out

larchie · Joined: 19 Jun 2003 Posts: 297

Presumably you were measuring over 750 cc after the fuel filter and so the fuel filter is good.

Here's the procedure for Cleaning the Air Flow Sensor and here's a thread on No Fuel Out of Injectors with suggestions on what to try.

spandelly · Joined: 26 May 2012 Posts: 23 Location: Manchester England

I'm going to change the fuel filter anyway so no worries there. I didn't really want to take the fuel dizzy off but the one that's now on the car is a replacement but I think I may have to clean it out bit by bit.
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It could always be worse so don't worry about it and get the spanners out

larchie · Joined: 19 Jun 2003 Posts: 297

Something else which is less likely since you already pulled two injectors would be to test t either one of those injectors with compressed air to make sure they-re not clogged with sediment or rust from other parts of the fuel system.

daniel · Joined: 18 Jun 2009 Posts: 686 Location: Sydney, Australia

This is normal. When you removed the injector you created a huge vacuum leak which has stopped the plate in the fuel distributor from lifting and pumping any fuel to the injectors.
If you want to test the injectors in the manner you have describe, jump the fuel pump and remove the rubber boot from the fuel distributor, then lift the plate by hand. Fuel should now come out in proportion to the amount of 'lift' you have applied to the plate.
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Over the top of skyline, total brake failure.... hit the wall at over 200 kp/h at the dipper, so anyone who has to brake for the esses is a pussy.
1977.5 Race Car, CAMS Group S Spec
1989 944 Cabriolet

larchie · Joined: 19 Jun 2003 Posts: 297

As daniel outlines and going by Hanes, I think the sensor plate only can be used to activate the fuel pump on pre-'79 924s, and so if the car is a later model, '79 and above, fuel output can be tested by jumping terminals 30 and 87 at the fuel relay position (with an inline 8 amp fuse for safety) and this should produce 750 cc or more in 30 sec through the removed fuel return line from the fuel distributor the line having been placed in a large measuring container beforehand.

Hanes cautions to disconnect the alternator whenever running the fuel pump with the engine off so as not to burn out the alternator diodes. I didn't see this caution in the 924 Workshop Manual but it's probably best to do so and be safe.

Certainly testing fuel output from the distributor return line should be done before such procedures as taking apart and cleaning the air flow sensor or the pressure valves in the mixture control unit or any of the other logical troubleshooting routines detailed by Hanes.

Hanes says that if 750 cc or more is not had in 30 sec. from the fuel return line the problem lies solely with the fuel filter, accumulator, or the fuel pump. Of course, if you do get the required amount, then his fault-finding tests involve working though the components in proper sequence until you get to the injector-output.

spandelly · Joined: 26 May 2012 Posts: 23 Location: Manchester England

Thanks for the replies guys. I didn't check the amount of flow due to not having a measuring jug bar the one in the kitchen and the wife would chop off my manhood if I used that. I did wedge the plate open and tried cranking it over and it was just a dribble so I don't think I have enough pressure.

I will buy a measuring jug and clean the injectors anyway but I think the pump might be duff. It is a bit noisy so probably isn't putting through enough pressure but I will test it tomorrow and see what happens.
_________________
It could always be worse so don't worry about it and get the spanners out