Inconsistent fuel pump
Turbo Mini Forums

Hi I have a bosch 044 fuel pump and when the ignition is switched on two clicks the pump runs but kinda wavers? Like it isn't running at full speed constantly. Is this normal?

Also I have the aeroquip fittings on everything, should I have used anything to seal on the 1/8 npt tapered threads? Because I have a few leaks I'm struggling to stop

Cheers

Dave the Cake

Explain your setup better. And what vehicle etc it is ?

044 is a 700hp capable pump...maybe worth baring in mind if using it on an engine that needs nowhere near that amount of flow, and pipes etc arent capable of providing it with adequate flow/supply of fuel.

Where exactly are these NPT fittings and what materials ? as the 044 does not use them.

And 1/8" NPT leaves a fairly small inside diameter, maybe not best matched to an 044 depending on where these fittings are.

But yes NPT fittings can be unreliable and the likes of PTFE paste or a similar sealant is often required. PTFE tape is not recommended as the tape can break up and get places it shouldnt get to.
Although I'd say if very careful with the tape it should be ok.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Thanks for your reply.

This is a mild turbo a series using the rising rate metro turbo fuel pressure reg.

Ok this is the fuel pump

http://bit.ly/13XcjvD

I wanted a pump with a larger inlet as I am running this gravity fed I have the pre pump filter to go with this and also a high flow inline filter after the pump.

It says this pumps operating pressure is 43psi which I felt gave me a safe margin after boost pressure in the carb/idle pressure/pressure drop over the circuit.

Everything after the pump is braided teflon fuel hose so I have the suitable -6 and -8 fittings with olives. -6 is the supply to the regulator and carb. -8 is the return line into the top of the fuel tank.

I drilled and tapped the metro regulator with the 1/8nptt to -6 fittings. The bore of the adapter is the same as the standard metro push on fittings. (The push on fittings are not useable with the teflon hose) 1/8npt was the largest I was willing to drill and tap the carb/reg

I have used teflon fuel hose because my fuel lines run through the cabin. And rubber lines emit fuel vapour smell in an in closed space. As the car is sat very low I did not want to run the risk of scraping them over speed bumps.

When you initially start the fuel pump it sounds fine but after a few seconds (presumably after it's built up pressure) that's when it wavers.

Sorry if my post comes across defensive, I spent a long time researching and finding the right bits and have frankly ran out of patience with it!

Cheers

Dave the Cake

Forgot to add- I have set the fuel pressure reg to provide 4psi of fuel to the carb at idle

Dave the Cake

That's a cheap copy pump, so cant comment on it's abilities or reliability.

The pump does not have an operating pressure as such. Pressure is dictated by the pressure regulator.

All such pumps need to be gravity fed ( or pumped I guess ). Any pre filter must not pose a restriction. What filter have you used ?

When you say olives...I assume you mean proper fittings designed for the teflon hose. Not just a compression olive on the outside of the teflon part ?

Drilling and tapping the regulator was always going to be a bad job. Fairly sure I said that some time back

But with suitable sealant on the NPT threads it should work. I'd also prefer to use a steel NPT fitting simply as it's stronger.

Can you post a soundclip of the actual noise ?

Most likely cause of noises with any efi pumps are a supply restriction in the feed to the pump.

Edited by stevieturbo on 21st Apr, 2014.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

are we sure its simply not a sticky fpr? ive had a sticky one and the fuel pressure would bounce around and affect the noise of the pump

Yes i moved to the darkside

Instagram @jdm_brett

This is the pre pump fuel filter

http://bit.ly/ZApS7X

Torques assured me this was perfectly adequate for the job. The pipe from the bottom of the tank feeding that filter has a bore of 13mm.

I don't quite understand what you mean by correct compression fittings?

I have these-


Which are sold with the olives for the size teflon hose I've used.

I don't have an issue with any of the hose joins leaking they have worked perfectly.

I will assemble the all again with some wurth chemical resistant sealant this evening, I'll give that a day to dry before running it again though. I will then film it

Thanks for your help

Dave the Cake

I personally would never use a pre-filter that small for a high flow pump. But it probably would be fine, others seem to use them ok.

The olive is purely the part that compresses over the outside of the teflon. ie the little silver bit inside the full fitting, hence the query.

Obviously if you are using the full and correct fitting, then there is no problem.

When you tapped the NPT threads, the fittings do actually screw in tight, and you havent tapped them too deep so the threads never actually tighten up like they are supposed to ?

It can be easy to do. Some thread sealant suitable for petrol should make a good difference though

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I really struggled to find a filter with a large bore which I assumed nessesary for the pre filter? So when they told me it was made for the job I ended my search there! Ha

Yeah I was careful not to tap too far, the adapter progressively tightens certainly doesn't feel like it's bottoming out on anything.

Fingers crossed this thread sealant works. If it doesn't I found a plastic padding cement type stuff that claims it seals leaks on petrol tanks, radiators etc so I may resort to trying that and accepting they will never come out again. Otherwise I guess I'll be buying another regulator and trying again.

Dave the Cake

In the case of those regulators, PTFE tape should be ok.

It's easy to take the regulator apart to see if any tape has broken off inside the tapped hole.

Plus it would be easy to run a small filter between regulator and carburettor, so it shouldnt be a problem.

But try the sealant first.

It isnt so much a large bore that's needed, it's filtration area

And within the confines of a small housing....well, you cant have a huge filtration area. And as you're using it in a setting where it is continually flowing 300 litres per hour ( genuine 044 figures ), that's moving some serious fuel.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Good news! Granville thread lock petrol resistant stuff has done the trick! No more leaks.

Here's a vid. Also once the engines running the pump runs fine at a constant speed

http://youtu.be/HSGvfhirbAg

Cheers for your input Steve

Dave the Cake