Fuel cavitation/Vapour lock

[Kitika]

G'day,
Having a few little issues with my ls1's fuel system. I've got the original 80 series diesel tanks with a holley 200L/H pump mounted on the chassis right beside it which feeds an 044 and regulator up in the engine bay. I'm getting noisey fuel pumps followed by surging and almost complete shut down after long runs (30 minutes cruising on open road). I've since filled the fuel tank completely and the pumps are still noisey. I got under the car and noticed that the plastic pre filter before the holley pump has bubbles forming on the filter element it self. Is this fuel cavitation? If so how do I get rid of it???

[chimpboy]

It sounds like you might need a fatter pipe to the holley.

But... how is your fuel circuit setup? If you are returning straight from the regulator to the tank, that might not be optimal; you could tee your return line in just before the holley instead.

[me3@neuralfibre.com]

G'day,
Having a few little issues with my ls1's fuel system. I've got the original 80 series diesel tanks with a holley 200L/H pump mounted on the chassis right beside it which feeds an 044 and regulator up in the engine bay. I'm getting noisey fuel pumps followed by surging and almost complete shut down after long runs (30 minutes cruising on open road). I've since filled the fuel tank completely and the pumps are still noisey. I got under the car and noticed that the plastic pre filter before the holley pump has bubbles forming on the filter element it self. Is this fuel cavitation? If so how do I get rid of it???

Holleys are noisy things. Might want to try something else.

Is there a return line? If yes - is it smaller than the main line? (it should be).

What pressure is the regulator set to?

Why isn't the motor EFI?

Paul

[chimpboy]

Why isn't the motor EFI?

It isn't EFI?

Kitika can you give more of an idea of your setup and the plumbing etc?

[want33s]

044 (Bosch) pump suggests it is EFI...

Sounds to me like the tank isn't breathing and the pump can't get fuel once there is a great enough suction built up in the tank...
When it conks out after 30 minutes driving does air rush into tank if you remove the filler cap?

[chimpboy]

Sounds to me like the tank isn't breathing and the pump can't get fuel once there is a great enough suction built up in the tank...
When it conks out after 30 minutes driving does air rush into tank if you remove the filler cap?

Good call, drive it with the fuel cap slightly loose maybe and see what happens.

[ferrit]

diesel fuel caps are non vented.

[Kitika]

It sounds like you might need a fatter pipe to the holley.

But... how is your fuel circuit setup? If you are returning straight from the regulator to the tank, that might not be optimal; you could tee your return line in just before the holley instead.

Yes I am returning straight to the tank/s. The inlet pipe is 3/8 and the return is the next size down. If I linked the return line into the piping just before the holley lift pump would that disrupt it's suction from the tank? The fuel tank actually pressurises instead of getting a vacuum like it used to with diesel. At the moment the cap is only half on to prevent the pressurisation (still need to hook up carbon canister etc for the breathing).

It is efi. It is a stock standard VY LS1. My setup goes like this.
Fuel tanks-plastic prefilter-holley pump(sitting slightly below the tank)-efi filter-bosch 044-regulator splits lines into return and motor feed set on 58 psi.
The efi filter onwards is high in the engine bay and the holley etc is at the back by the tank. I have removed the efi filter for now to see if it makes a difference to the 044's noise but it doesn't as the bubbles most only be coming from down below? I will be putting the efi filter on the high pressure side of things when I sort out this problem.

[nayto]

theres nothing funny about vapour lock

[Kitika]

Took the car out for a spin to see if changing the prefilter and removing the efi filter would change anything.
Not getting any vapour lock/surging now and seems to be running fine altho it is only about 20*C so everything is running alot cooler.
The 044 is running very quiet now I removed the efi filter from infront of it but the holley pump is getting progressively louder... The plastic pre filter still has a huge amount of bubbles coming through it too? Checked the hoses and they all seem to be tight so don't think it is an air leak.

[me3@neuralfibre.com]

If there is a screen in the tank it could be blocked. That woul draw vacuum and cause vapour in the prefilter. Could be crap from diesel washed free by the petrol.

Paul

[Kitika]

I put a tee piece in so the return is going back to before the first pump as well as the tank and that seems to have stopped the problem altho today was about half the temperature than the last week so I'll have to wait to see if it still works in 40* heat. Thanks for the help fellas!

[me3@neuralfibre.com]

I put a tee piece in so the return is going back to before the first pump as well as the tank and that seems to have stopped the problem altho today was about half the temperature than the last week so I'll have to wait to see if it still works in 40* heat. Thanks for the help fellas!

I think that proves the pickup in the tank is blocked - now it can get fuel it's not pulling as much vacuum.

Paul

[Kitika]

It could be but it never had the problem before with the old 1hz? I was thinking the 200L/H pumps are just drawing to much fuel through for the 3/8 pipe or the slightly higher pressure returned fuel is too close to the pickup so the hot aerated fuel is being sucked straight back into the pickup?
Do you know where the screen is in the 1hz tank if there is one? I can't remember seeing one in the manual.

[chimpboy]

I was mulling your problem over and I don't know what the issue is really, but two things you are doing different... not saying they're wrong but they are not the usual arrangement. One is that you are not running a surge tank, and the other is that the 044 normally has bigger pipe going in, say 1/2".

The other thing is that I have never heard anyone saying a good thing about the Holley pumps. They are reportedly junk - I am just repeating what I've heard as I've never used one but it makes me wonder.

I really wonder if you should get a surge tank above the EFI pump.

But then again all this might just be masking the problem Paul is talking about. A blocked screen on the pick-up is very common.

[me3@neuralfibre.com]

Why can't you move the EFI pump to the back and suck from the tank directly?

I agree with chimpy - Holley is noisy and problematic in my experience.

Why else would race cars need a "spare" pump plumbed in? (always had me buggered).
Then again - I did race a gemini

Paul

[Kitika]

I tried swapping tanks etc but it didn't seem to help so i'm assuming it was caused by cavitation from the filter/s and pump heat unless I have two blocked pickups which is possible as it has been sitting for about 6months with minimal diesel in the tanks. (altho the filter looks pretty clean)
Had to pour water over the 044 to cool it so I could continue driving on saturday (that was before I put the t-piece in).
The 044 is almost silent in operation now but the holley is loud as! I have read and found out they are rubbish pumps after I bought it... So i'm on the look out for something quieter maybe a carter pump?
As for surge tanks you can prove me wrong as this just my understanding but diesel tanks have built in surge tanks as the injector pumps can't get air bubbles in them if they are going to run properly? That is why I didn't bother putting a surge tank into the system for now but I may do if I can't get rid of this problem.
Another quick question if I were to put a surge tank in do you return the fuel from the regulator in to it or does that go back to the tank and a separate return has to be used on the surge tank back to the fuel tank?

[Kitika]

That is another option put the 044 by itself down in the holleys place. If it is mounted below the tank line will it have enough suction to get a siphon happening? Would it still go ok if I went on some fairly severe angles etc?

[chimpboy]

Another quick question if I were to put a surge tank in do you return the fuel from the regulator in to it or does that go back to the tank and a separate return has to be used on the surge tank back to the fuel tank?

The surge tank has four connections. Basically what you end up doing is running two separate loops. One is your fuel tank -> lift pump -> surge tank -> return to fuel tank, which keeps the surge tank full. The other is your surge tank -> 044 -> fuel rail -> return to surge tank which keeps the fuel rail pressurised.

The surge tank would have the nice big outlet for the 044 as its lowest connection. Remember you are circulating 200 litres per hour with the EFI pump but you are only actually using a fraction of that. So when you have a surge tank it doesn't matter if your holley is keeping up with the 044. But because in your case you just have them in series, if the 044 is much gruntier than the holley then you could have issues (but I don't see how it would cause the issue you're having).

That is another option put the 044 by itself down in the holleys place. If it is mounted below the tank line will it have enough suction to get a siphon happening? Would it still go ok if I went on some fairly severe angles etc?

If you can fit the bosch pump below the fuel tank then that is basically your fix imho. Especially if as you say the diesel tank has a built-in surge section anyway.

The efi pump doesn't so much want to suck as to have a nice big gravity-fed pipe going into it. This pipe can be your fuel return as well, I am pretty sure I've seen some factory setups where the efi pump pick-up is also the fuel return.

[Kitika]

I might try the 044 as the only pump then with the t-pieced return because the holley is embarrassingly loud! Both pumps are rated at 200L/H so they should be keeping up together. Only thing with running the 044 as the only pump is that it'll have to suck the fuel through the prefilter as well but it's worth giving it a test run down there.

The surge tank has four connections. Basically what you end up doing is running two separate loops. One is your fuel tank -> lift pump -> surge tank -> return to fuel tank, which keeps the surge tank full. The other is your surge tank -> 044 -> fuel rail -> return to surge tank which keeps the fuel rail pressurised.

The only problem I have with that setup is the fuel would eventually get hot from heat soak and from being pumped around so often with out a large mass of fuel (fuel tank) to cool it off and possibly cause the cavitation again. But I guess I can only keep experimenting with it.

[chimpboy]

The only problem I have with that setup is the fuel would eventually get hot from heat soak and from being pumped around so often with out a large mass of fuel (fuel tank) to cool it off and possibly cause the cavitation again. But I guess I can only keep experimenting with it.

Nope, it is still circulating to the tank. It's just that the surge tank allows the two pumps to be pumping different volumes without affecting each other.

The holley (or whatever) would still be circulating fuel from the fuel tank to the surge tank and back. The 044 would be circulating fuel from the surge tank to the fuel rail and back. It's still all the same fuel so the fuel from the rail/engine goes back to the fuel tank, with the surge tank as a sort of buffer for differences between the two pumps (eg if the lift pump is pissweak, or when the lift pump loses fuel on a steep angle, hard cornering, etc).

Have a look at this, it will make more sense:

[Kitika]

Ah yes of course! Oooops I was thinking if it was using a little 50L/H facet pump or something similar it wouldn't have enough cool fuel coming up to cool of the hot fuel but that'd work good. That makes much more sense! I'll try the 044 down the bottom first as thats the cheapest option and easiest if it does work out. Otherwise i'll have to fab up a surge tank.
Cheers mate you been a great help!

[me3@neuralfibre.com]

Not sure if you really need to go to the trouble.

How does the OEM car work? - copy that.

Paul

[PGS 4WD]

Get a Carter pump as a lift pump and feed it into the 044, 044's are notoriously noisy, make sure all pumps are rubber mounted. 044's were were designed in the 70's for CIS injection systems, there are better, quieter, lower current draw, higher output pumps available now.

Joel

[Kitika]

The 044 is pretty much silent now but what high pressure external pumps do you recommend?

me3@neuralfibre.com

How does the OEM car work? - copy that.

Paul

I would use the factory commo pump but modifying the 2 tanks looks like too much hassle. I do have the commo pump tho if I need to go down that path.

[-Scott-]

Not a 4wd, and a smaller engine too, but I've EFI'd my daily driver Sigma, and only have the one fuel pump (aftermarket VL external pump) sucking from the original pickup and feeding into the original metal fuel line which runs under the car.

I thought I'd get the system running without the surge tank, and add the lift pump/surge tank when I got sick of problems.

I haven't had any problems. But I don't throw it around the hills like I used to, either.

[chimpboy]

Not a 4wd, and a smaller engine too, but I've EFI'd my daily driver Sigma, and only have the one fuel pump (aftermarket VL external pump) sucking from the original pickup and feeding into the original metal fuel line which runs under the car.

I thought I'd get the system running without the surge tank, and add the lift pump/surge tank when I got sick of problems.

I haven't had any problems. But I don't throw it around the hills like I used to, either.

I did the same (same pump even, I think) but have since fitted a lift pump and a surge tank. I don't know if it makes any difference, the situation I wonder about is where you get a drop in rail pressure for a moment due to fuel sloshing around in the tank (uncovering the pick-up). Could you be running lean every so often without knowing it?

I don't think it really matters much but I got a small surge tank cheap so I did the upgrade.

[-Scott-]

Could you be running lean every so often without knowing it?

Probably - but meh, just call me lazy.

If it was a high compression motor running super-advanced ignition and working hard all the time I would be more inclined to worry. As it is, I'm happy to convince myself that any lean periods would be of very short duration, and unlikely to cause signficant damage any time soon.

If I ever re-gain the enthusiasm to find the power which should be there I would probably install a surge tank too.

[str8up]

Sorry to sort of hijack this thread but I would like to know if a 6mm return line is big enough for an 044? (a 10mm line is feeding it)