Fuel pump(s) not pumping

[citybreeze]

Hi again. New day new problem,

I'm having a problem with fuel pumps this time, in that they are refusing to pump any fuel when the engine is running. Both work fine on the external primer lever. 

The first pump was working ok, until I took it off to renew the fuel lines, and I decided to clean and overhaul the pump. Back on the car, it worked fine when pumped manually, but was not doing it's job with the engine running. I assumed I'd cocked up the overhaul somehow, so bought a new one.

Same deal with new pump. I can pump fuel using the manual lever, but it won't run off engine power.  

Both have the same shape rocker arm to run off the cam.  My initial thought was that I'd fitted the pumps incorrectly so the rocker arm was not engaging,  but after some fiddling it looks like there is only one way they fit.  Hook it under and bolt it in place. 

I don't know how I check whether or not the rocker is engaging with the cam, any tips? 

 

[Adrian Cooper]

Hi Citybreeze,

 

I took off and replaced my fuel pump last week and I don't remember hooking it under the cam, I think it runs on the other face. Certainly the shiny wear patch on the lever would suggest that it goes this way. 

I'm sure one of the real experts will be along soon but I would be tempted to try it the other way.

Good luck!

Adrian

[Pete Lewis]

They certainly dont hook under the cam the lobe has to push the lever , not pull it 

So must be cam lobe  ...pump  lever...block face   never   pump lever... cam  .... block face

 

Pete

[NonMember]

What engine?

As Adrian says, the pump doesn't "hook under" the cam, though it does have to be inserted through the block aperture in an upward direction.

There are at least three different lever angles across the production range. It's unlikely you've changed that, though. The gotcha is that late 1500 pumps are angled to require a spacer behind the pump, and if you fit that spacer to an earlier pump then it just won't work.

[citybreeze]

It's a 1300 'FD' engine.  No spacer block with either pump as far as I can see.

Is the gap between the cam and the inside of the block quite narrow? As in, should it be a bit difficult to push into place?

I'll have another go tomorrow, and I'll try to hold the rocker arm in as close to the inside of the block as possible this time. 

Thanks for all the help. 

[Pete Lewis]

Generally there is some spring load which you need to push the pump up to the block ,   showing the lever is riding on the cam lobe

Pete

 

[AidanT]

As others have said the lever need to be in front of the cam 

Feed the lever in to the apperture of the block

Once in, lift the pump upwards so the lever is touching the top of the apperture 

Then move the pump so the faces touch

Then slide the pump downward to align the bolt holes

Sorry for the description, but I could not think of a word to describe the movement 

Aidan

[Pete Lewis]

In  ..... out .....or is that Dougs other forum  !!!

Pete

[AidanT]

That's definitely Doug's other forum!!

Aidan

 

[citybreeze]

I removed the new pump, and the rocker lever is snapped off (see picture) and is probably sitting somewhere in the base of the block (hopefully well out of the way).  That'll explain why there was no pumping, I must have fitted it wrong and broken it.

I put the original pump (recently overhauled) back on, using the directions above, and everything is working. 

I still have the original problem however, which is a lack of top end acceleration and power under load.  It accelerates well in 1st and 2nd up to about 30/40mph.  Trying to pull from 30-50 or accelerate above 60 results in some hesitation, or a slight misfire/backfire type lurch and pop, and little to no increase in speed. 

The engine runs beautifully and revs well on the driveway  and is set to the right mixture according to my colourtune.

While the pump is working, i can never see much more than a fast trickle coming through at that the in-line filter immediately after the pump.  So I'm concerned that not enough fuel getting through might still be the problem.  Recently replaced all fuel lines, cleaned the tank, and replaced with fresh v-power. I'm fairly sure the fuel isn't stale, as I got it at a service station Shell off the A1.  I reckon they sell quite a bit of it. 

I recently re-replaced the manifold gasket and sealed with blue Hylomar, and sealed the carb/manifold joint with loctite 574. No evidence of any leaks at either when spraying around those areas. 

Recently cleaned and regapped all the plugs (only a month old anyway), have a new Bosch coil, new vacuum advance unit and hose, checked all points, rotor arm, etc.  Refitted my old condenser too, didn't make a noticeable difference.  Can't find any problems on the ignition side.  

Other than a weak fuel pump, could there be any other reasons for this lack of power? 

 

[Pete Lewis]

Some plastic filters compress when tighten  hose clips and the spouts collapse making fuel restriction possible.

Have you checked the float needles are clear , what air filters are you using   pancakes or std airbox  ( I dont remember)

Pete

[Paul H]

Is there a way of measuring out put from the fuel pump which I think should be up to 3.5 psi ?

Paul

[Anglefire]

I have a gauge that does vacuum, fuel pressure etc. So yes you can measure it. 

[citybreeze]

I have a couple of in-line plastic fuel filters,  one in the boot just after the tank, one just after the pump.  They were cheap eBay items, and I do remember thinking the internal diameter looked a little bit smaller than it should, even before I clamped them in place.  I'll whip those out and replace with a short section of copper line to see if that improves things. If so, I'll get filters with metal spouts. 

I've checked the float needles, and flow seems good.

I have a pair of K&N pancake filters fitted. I have fitted the richer H6 needle and yellow springs to suit. 

I recently replaced both jets, but the problem existed the same before I did that. 

As for pressure, I have a vacuum gauge somewhere which might do fuel pressure. I'll dig it out later and have a look.  I know it's hard to do visually, but it doesn't look like it's kicking fuel out with much force (viewing at entry to fuel filter) when I rev it, but it revs well. Obviously I can't see what's going on when it's under load though!

So to start with, I'll swap out the filters and replace with (another) new pump to see if anything changes. 

[Paul H]

17 minutes ago, Anglefire said:

I have a gauge that does vacuum, fuel pressure etc. So yes you can measure it. 

Would you dry test or allow petrol to be used 

Paul

 

[Anglefire]

I haven’t used it in that application, but given it’s specified for fuel pump testing I would use it with fuel. 

[Pete Lewis]

Makes no odds whats in the pipe to the gauge air or fuel the psi is the psi   

Its flow you need as much as psi.   With it idleing you should get a well defined squirt and get a cupfull in a few seconds of running

Before the floats die out 

Pete

 

[NonMember]

11 hours ago, Pete Lewis said:

Makes no odds whats in the pipe to the gauge air or fuel the psi is the psi  

Well... yes and no. It should measure the same, although compressibility has a bearing on it, but you need to be sure there's nothing in the gauge that can be chemically attacked by petrol. Like the pump in a Clarke parts washer, that's made of a plastic that goes brittle on exposure to petrochemicals.

[dave.vitesse]

This is a long shot but water in the petrol can also cause this problem. Most pumps will not pump a combination of water and petrol if they are near equal. If unknowingly you have filled up with contaminated fuel this may be the cause.

The water sits at the bottom of the tank if the fuel is getting down to below a half tank drain off a sample into a clear glass jar. Leave this for a couple of hours then see if there is any water present. The water will not mix with petrol and if present can be see at the lower part of the jar.

Dave 

[Nick Jones]

On 7/22/2018 at 5:25 PM, citybreeze said:

I still have the original problem however, which is a lack of top end acceleration and power under load.  It accelerates well in 1st and 2nd up to about 30/40mph.  Trying to pull from 30-50 or accelerate above 60 results in some hesitation, or a slight misfire/backfire type lurch and pop, and little to no increase in speed. 

The engine runs beautifully and revs well on the driveway  and is set to the right mixture according to my colourtune.

Does sound like it's going lean under load.  Might not be fuel starvation due to the pump though as that will normally give you some "go" in the short term and then die off as demand outstrips supply and float chambers empty.

Quick and dirty test - pull the choke out when it's faltering/holding back.  If it then pulls away and keeps on pulling it is simply going weak under load due to the wrong needles or incorrect setting.  This might be because:

- You used a Colourtune.  My experience with these and SUs is that if you get a nice blue colour at idle it'll be too lean everywhere else.

- You have non-standard air filters and/or exhaust system so the engine is flowing more air and the standard needles are now wrong for it.

- You have the wrong needles fitted.

- Dashpot springs are missing or the incorrect ones (too light)

Nick

[citybreeze]

3 hours ago, Nick Jones said:

Does sound like it's going lean under load.  Might not be fuel starvation due to the pump though as that will normally give you some "go" in the short term and then die off as demand outstrips supply and float chambers empty.

Quick and dirty test - pull the choke out when it's faltering/holding back.  If it then pulls away and keeps on pulling it is simply going weak under load due to the wrong needles or incorrect setting.  This might be because:

- You used a Colourtune.  My experience with these and SUs is that if you get a nice blue colour at idle it'll be too lean everywhere else.

- You have non-standard air filters and/or exhaust system so the engine is flowing more air and the standard needles are now wrong for it.

- You have the wrong needles fitted.

- Dashpot springs are missing or the incorrect ones (too light)

Nick

There is still a little bit of 'go' before the power splutters away, until I'm going about 60mph, then any further pressing of the accelerator doesn't do a lot.

I'll try pulling the choke out next time I take it for a drive to see what happens.  I'll maybe set the carbs to be a little too rich as idle too, to see if that evens things out further up the range. 

As for the needles and springs, I have fitted the stronger 8oz Yellow springs and 'H6' needle as Moss recommends for use with upgraded filters. 

One thought I had though: I have fitted higher flow air filters, but still have the standard diameter exhaust system fitted.  Will this cause a problem with too much back pressure? Maybe the exhaust can't be cleared through the narrow pipe in time and is affecting the combustion of the next cycle at higher revs? Or am I overestimating just how much air can be pulled through a set of pancake filters?  The exhaust on there is fairly new, So I hadn't planned on upgrading until I'd had a little more use out of it!

I've also ordered a new pair of float needle valves.  The current ones seem fine to my (uneducated) eye, but can't hurt to swap in some new ones to see if that makes any difference. 

[Anglefire]

I have the WinSu program - and it recommends ABM needles and red springs - assuming the rest of your engine etc is standard. (ABM are very similar to H6.)

[Pete Lewis]

The first two stages of the needle profile are always the same whatever the needle number, the profile only changes from position 3 

1 and 2 are constant hence you can set the idle with the piston  down but be way out for your required Running positions

as the piston rises further. 

[citybreeze]

11 hours ago, Anglefire said:

I have the WinSu program - and it recommends ABM needles and red springs - assuming the rest of your engine etc is standard. (ABM are very similar to H6.)

 

2 hours ago, Pete Lewis said:

The first two stages of the needle profile are always the same whatever the needle number, the profile only changes from position 3 

1 and 2 are constant hence you can set the idle with the piston  down but be way out for your required Running positions

as the piston rises further. 

I have the AUD257 carbs fitted to an otherwise standard FD 1300 engine, standard exhaust.

The SU website has the red springs (6oz?) listed as standard equipment, which is why went one up to the 8oz Yellow springs. 

The original equipment needle is listed as BO type, and I believe the H6 was listed as one up from this, reccommended for use with free flow filters and uprated exhaust. 

Maybe the H6 needles are still not rich enough? Is the ABM needle richer towards the top end (position 3) than the H6?

Is it worth getting 2 or 3 pairs of progressively richer needles, and using trial and error to get the best match? Or does anybody have a needle they'd reccommended based on their personal experience, as listings from different sources seem to reccommended different setups. 

[Anglefire]

I've compared the three needles and the H6 is the richer of the three.

TBH, with just a filter change, I wouldn't expect you too need radical needle changes.