MK1 CIS fuel supply

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Hilltop
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MK1 CIS fuel supply

Post by Hilltop » Thu Feb 21, 2019 7:40 pm

Hi, having problems getting my Mk1 Storm to run properly due to insufficient fuel supply. When restoring the car I renewed the filler neck, fuel pump (Bosch - however it had been in storage for a few years), filter and tank and cleaned out the pipes, however it runs poorly and is down on power. Read a bit about the k-jet injection system and had a look at the Haynes manual.

I fixed up a wire, with switch, to bypass the relay and wired in a multimeter. When running the pump was pulling 6.3 amps which is within spec. I also measured the electrical supply to the pump - it was 12 volts, 0.5 less that the battery. Then I detached the return pipe from metering head and measured the fuel that was being supplied from the pump in 30 seconds. It was 700ml, and Haynes say this should be a minimum of 900ml.

Can anyone suggest what's causing the fuel flow problem ? Also, why is the flow measured on the return to the tank and not on input ?

Thanks for any help and suggestions !



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james butler
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Re: MK1 CIS fuel supply

Post by james butler » Fri Feb 22, 2019 7:32 pm

could be the pump has an internal leak?


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blakey
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Re: MK1 CIS fuel supply

Post by blakey » Fri Feb 22, 2019 9:27 pm

Lack of use, dirt and moisture ingress are k-jet killers.

It's worth carefully removing the System Pressure Regulator in the fuel distributor, these can stick with dirt or corrosion from moisture in the fuel.

There's a lot of info on the web for K-jet, but this site has some good info and how to's half way down the page:

http://www.cabby-info.com/fuel.htm

Mine was stood around for years and the Warm Up Regulator had seized due to corrosion, so had the same control pressure hot or cold, this cause poor performance, economy and emissions.


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mark1gls
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Re: MK1 CIS fuel supply

Post by mark1gls » Fri Feb 22, 2019 9:47 pm

Have you pulled out the fuel injectors and checked the spray pattern and how much fuel is coming out of each injector.
Injectors don’t last forever but there’s a few more things to check/test before just replacing parts...


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Hilltop
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Re: MK1 CIS fuel supply

Post by Hilltop » Fri Feb 22, 2019 11:10 pm

Thanks for all the suggestions, lots of good info on link by blakey.

The below spec fuel supply must be a clue to the problem. To try and narrow things down what I'm trying work out is - could something in the metering head or incorrect system pressure be decreasing the amount of fuel returned to the tank or is it down to a problem with pump/accumulator or tank.



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Re: MK1 CIS fuel supply

Post by mark1gls » Sat Feb 23, 2019 10:12 am

The accumulator can be tested by unscrewing the little screw on the back, if petrol comes out the hole then it’s shot. The accumulator holds the fuel pressure in the system so when faulty it’s takes some cranking of the engine when hot as the pressure need get back up.

A pressure test of the injection system is probably the easiest way to find/check for faults, you can buy a kit but it’s expensive, I’ve seen people make a home made kit search Bosch k-jet pressure kit...


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blakey
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Re: MK1 CIS fuel supply

Post by blakey » Sat Feb 23, 2019 11:05 am

I'd recommend getting a pressure test kit too. I bought a cheap one and had to modify a few bits to connect it to the metric connections on the metering head. You can check the condition of the pressure regulator in the metering head and also ensure that the plunger has free movement, and is clean not corroded or scored.
A word from experience, do not be tempted to split the two halves of the metering head, it is very hard to get it to seal again afterwards.
In fairness, the issue you have will likely be with the pump, fuel lines, pressure reg in metering head or the warm up valve.

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Hilltop
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Re: MK1 CIS fuel supply

Post by Hilltop » Thu May 02, 2019 9:44 pm

Quick update on this. Left car for a few months and started fiddling again a few weeks ago. Emptied tank (found to be clean), renewed pump and cleaned out main pressure regulator - no change ! So then took advice and looked for a pressure gauge. Managed to get a proper Bosch one on an auction site and did the tests. With tap closed system pressure came up at 5 bar which is within spec, opened tap to get control pressure and no change ! Hot or cold there was no change in control pressure. I then removed the fuel line return from the warm up pressure regulator and no fuel came out and no change in pressure.

Although I had cleaned the WUR once before I tried again - but pressure results were the same. I was fairly sure the WUR was at fault now so I searched online and managed to find a NOS one which matched the original part number - was quite expensive but cheaper than refurb. This arrived and went straight on the car. I tested system pressure -5 bar and then with tap opened the pressure went down to 1.5 bar and rose steadily to 3.6 bar. I have yet to take the car out on the road but things are looking good ! Thanks for all the advice - indeed pressure gauges are the way to go if you have problems with k-jet.



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Re: MK1 CIS fuel supply

Post by mark1gls » Thu May 02, 2019 10:11 pm

Fingers crossed it worked.

The cost of buying the pressure gauge will probably be cheaper than just buying lots of new parts to throw at the k-jet system and hoping they work parts are getting expensive now..

Let us know how you get on.


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Hilltop
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Re: MK1 CIS fuel supply

Post by Hilltop » Sat May 18, 2019 7:44 pm

Annoyingly the new WUR did not sort this problem. As before it starts well hot or cold and idles fine but there is no power (although slightly better when cold). It will hardly rev over 2500 under load even if my foot's on the floor. If I stop the engine and then restart it seems to go better for a while but gradually worsens. Last effort was changing the coil and rotor arm (leads, plugs and dizzy cap are new BOSCH) but still no better. I've spent a lot of time on this now and renewed various parts - a bit fed up with it really. Not sure what to try next - possibly the fuel distributor - but these cost £400 to get refurbished !



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Re: MK1 CIS fuel supply

Post by blakey » Sat May 18, 2019 8:03 pm

If you haven't done an injector test, I'd do one before changing the fuel distributor. Carefully remove all four and set them up to spray into a container to check the spray pattern and flow. You could also do a quantity test. There are quite a few Jetronic guides on the web that detail how to do both tests.

Are confident that the cam and ignition timing is correct and the ignition distributor advance is working?

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chopperoli
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Re: MK1 CIS fuel supply

Post by chopperoli » Mon May 20, 2019 11:22 am

There is sometimes a tiny filter inside the banjo bolt on the metering head fuel inlet, meant to be removed at the car's first service but often left in. Easy to check and remove if it's there.

Also are you really sure it's not some other electrical problem still? If not I'd plan for a metering head overhaul