Fuel check valve LS7 needed?
Discussion
Hopefully an easy answer to this.
Given that you have the std factory pollock valve setup with LP pump feeding from the two tanks through to swirl-pot, and then from swirl-pot to HP pump via filters to pressure reg to rail (with the usual returns), then I have found that when the ign is turned on:
The LP pump fires into life (direct feed via relay so constant) - Good!
The HP pump fires into life (feed from ECU via relay) for a few seconds to pressurise system then stops - Good!
The pressure reg indicator winds up all the way around so good head of fuel - Good!
Then I notice that the regulator dial (sfter HP pump stops) quite quickly starts to drop to about 20psi. - Bad!
Now I have been messing around with the circuit and the only think I can think of is that I took out the one-way flap valve from the LP circuit (just before the swirl-pot), but this can't be so because the swirl-pot returns to the tanks via the pollock valves?
Prior to my messing around the fuel pressure did maintain a healthy high value on initial HP pump working even after stopping, and starting the car was not an issue. I have not messed with the HP circuit at all, just the LP circuit prior to the Swirl-pot!
It now will not start due to low residual fuel pressure I assume.
Probably an easy answer, but it is puzzling me!
Given that you have the std factory pollock valve setup with LP pump feeding from the two tanks through to swirl-pot, and then from swirl-pot to HP pump via filters to pressure reg to rail (with the usual returns), then I have found that when the ign is turned on:
The LP pump fires into life (direct feed via relay so constant) - Good!
The HP pump fires into life (feed from ECU via relay) for a few seconds to pressurise system then stops - Good!
The pressure reg indicator winds up all the way around so good head of fuel - Good!
Then I notice that the regulator dial (sfter HP pump stops) quite quickly starts to drop to about 20psi. - Bad!
Now I have been messing around with the circuit and the only think I can think of is that I took out the one-way flap valve from the LP circuit (just before the swirl-pot), but this can't be so because the swirl-pot returns to the tanks via the pollock valves?
Prior to my messing around the fuel pressure did maintain a healthy high value on initial HP pump working even after stopping, and starting the car was not an issue. I have not messed with the HP circuit at all, just the LP circuit prior to the Swirl-pot!
It now will not start due to low residual fuel pressure I assume.
Probably an easy answer, but it is puzzling me!
But the weird thing is, that before I messed with the LP side of things (there was a problem with the pump, and someone suggested that the flow was restricted by an in-line filter I had fitted), the HP circuit always maintained a very good pressure reading for over 10 mins after the HP pump stopped (after switching the ign on). Now it doesn't?????
Storer said:
I doubt the fuel is leaking back through the HP pump so I would be looking at your HP lines and the returns to tank for a leak or non-functioning pressure regulator.
Of course I could be talking bollo*ks.
Paul
My money would be on the regulator.Of course I could be talking bollo*ks.
Paul
Out of interest, how do you know the pressure is low? Are you basing this on the reading on the regulator itself?
No fuel leaks as such!
Must admit, this recent event seems rather odd to me. if the HP pump has 'charged' the rail to 60+ psi (think from memory) on initial ign on, and then the pump is at rest (no cranking), would you expect the Pressure Reg to register that same pressure for a while, but over a good few mins, slowly sink?
This is what I saw originally, but not now.
...so I suspect that either the Regulator is faulty, rubbish is in the line holding the valve open enough to leak back through the return, or that one of the injectors are leaking/ stuck open?
Would I be right?
Are there any other possible causes?
cheers
Must admit, this recent event seems rather odd to me. if the HP pump has 'charged' the rail to 60+ psi (think from memory) on initial ign on, and then the pump is at rest (no cranking), would you expect the Pressure Reg to register that same pressure for a while, but over a good few mins, slowly sink?
This is what I saw originally, but not now.
...so I suspect that either the Regulator is faulty, rubbish is in the line holding the valve open enough to leak back through the return, or that one of the injectors are leaking/ stuck open?
Would I be right?
Are there any other possible causes?
cheers
macgtech said:
My money would be on the regulator.
Out of interest, how do you know the pressure is low? Are you basing this on the reading on the regulator itself?
Yep! - as I said, all this worked fine for about a month. Pressure was up there on the gauge at maximum for quite a while. Now it goes up - then come down like a deflating tyre!Out of interest, how do you know the pressure is low? Are you basing this on the reading on the regulator itself?
I do hope its not the reg! I purchased this in 2008. The car is still not on the road, so despite this I presume it is well out of warranty!
Edited by V8 Vum on Thursday 11th August 15:17
Without an external leak the possible routes are...
Pressure reg not sealing properly.
HP pump non return valve not sealing.
Injector(s) leaking.
How long has the engine run since the install?
Although there are filters in the system dirt could have been introduced after them and still be working its way into undesirable places.
Steve
Pressure reg not sealing properly.
HP pump non return valve not sealing.
Injector(s) leaking.
How long has the engine run since the install?
Although there are filters in the system dirt could have been introduced after them and still be working its way into undesirable places.
Steve
Hi Steve,
I had it running regularly during tests about 3 months ago, until I encountered a problem caused by what appears to be my stupidity ie ran out of fuel and bxxxgered the LP pump. At the time, I thought there was another problem because the ECU was reporting a cam sensor failure, but actually it was fuel starvation, as proved when I refilled.
Then the thing ran fine for a week or so.. (started 3 times with no probs), the last time I was testing the radiator fans, and then more problems - ie the engine got to working temp, then coughed and stalled (no thottle response) and I could not restart (it just coughs and bangs).
It was then that I noticed the pressure anomoly - filled up again to be sure, gave up in disgust...had 3+ beers and a couple of whiskeys to be sure I would forget it.... and swore not to try to sort it until now - That was 3 months ago.
So I am mulling things over in my mind now to try to map a plan of attack to see where the issue is...
...any thoughts or test ideas would be gratefully received.
I had it running regularly during tests about 3 months ago, until I encountered a problem caused by what appears to be my stupidity ie ran out of fuel and bxxxgered the LP pump. At the time, I thought there was another problem because the ECU was reporting a cam sensor failure, but actually it was fuel starvation, as proved when I refilled.
Then the thing ran fine for a week or so.. (started 3 times with no probs), the last time I was testing the radiator fans, and then more problems - ie the engine got to working temp, then coughed and stalled (no thottle response) and I could not restart (it just coughs and bangs).
It was then that I noticed the pressure anomoly - filled up again to be sure, gave up in disgust...had 3+ beers and a couple of whiskeys to be sure I would forget it.... and swore not to try to sort it until now - That was 3 months ago.
So I am mulling things over in my mind now to try to map a plan of attack to see where the issue is...
...any thoughts or test ideas would be gratefully received.
The comment about fuel being present was slightly tongue in cheek!
Having said that - could it be that the pollack has failed causing no fuel to get through? My thinking is that if the HP pump is sucking air, it could well pressurise initially but gradually leak out over an extended period of time (which is what you are seeing).
Could it be that the pollack is stuck in the central position? I suppose you could check this by seeing if there is any fuel in the swirl pot.
Jonny
Having said that - could it be that the pollack has failed causing no fuel to get through? My thinking is that if the HP pump is sucking air, it could well pressurise initially but gradually leak out over an extended period of time (which is what you are seeing).
Could it be that the pollack is stuck in the central position? I suppose you could check this by seeing if there is any fuel in the swirl pot.
Jonny
Sorry, let me get this clear! The engine ran a few times after the replacement LP pump was fitted. During one engine run it got up to temp, spluttered and stalled and now won't start?
The FPR shows 60+ psi on initial prime but then falls away quickly?
It may be worth checking to see if the HP pump is running whilst cranking. Does the Regulator show decent pressure whilst cranking?
The FPR shows 60+ psi on initial prime but then falls away quickly?
It may be worth checking to see if the HP pump is running whilst cranking. Does the Regulator show decent pressure whilst cranking?
Checked my fuel pressure and it does the same, switch on ignition low pressure pump fires up (Holley blue top ratler 110gph) and then high pressure pump primes up to 58psi but then drops like a stone to zero, press starter and fires up immediately.
I don't have a pollock valve set up, just a Holley fed from both tanks which are connected by -12 hose, that feeds the swirl pot which in turn feeds the HP Bosch 044 pump. Fuel is returned to the swirl pot which in turn returns to both tanks via a T piece in the top balance hose. Whether that makes a difference I don't know?
Graham
I don't have a pollock valve set up, just a Holley fed from both tanks which are connected by -12 hose, that feeds the swirl pot which in turn feeds the HP Bosch 044 pump. Fuel is returned to the swirl pot which in turn returns to both tanks via a T piece in the top balance hose. Whether that makes a difference I don't know?
Graham
Keith,
I have managed to keep the pressure in the fuel lines by adding a non return valve (Speedflow
) after the Bosch 044 pump before the filter going into the fuel rails. It now holds 60lbs pressure for a considerable amount of time after the initial priming.
I have also added a non return valve at the top of my swirl pot to give the LP pump something to push against, as per your suggestion.
Graham
I have managed to keep the pressure in the fuel lines by adding a non return valve (Speedflow
) after the Bosch 044 pump before the filter going into the fuel rails. It now holds 60lbs pressure for a considerable amount of time after the initial priming.I have also added a non return valve at the top of my swirl pot to give the LP pump something to push against, as per your suggestion.
Graham
1st question: why do you care if fuel pressure is close to (or at zero) when the engine is not running?
2nd question: Why do you think that your regulator would be able to "hold" pressure at zero flow?? (most regs i have ever taken apart just use a metal on metal seat (for durability) so it isn't a perfect seal, and hence doesn't hold pressure with the pump off.
3rd question: the non return valve in HP pumps is generally just a ball bearing type, again, unlikely to be able to hold a "zero leak" pressure head.
I wouldn't worry about it, if you have the correct pressure with the pump running you're sorted ;-)
2nd question: Why do you think that your regulator would be able to "hold" pressure at zero flow?? (most regs i have ever taken apart just use a metal on metal seat (for durability) so it isn't a perfect seal, and hence doesn't hold pressure with the pump off.
3rd question: the non return valve in HP pumps is generally just a ball bearing type, again, unlikely to be able to hold a "zero leak" pressure head.
I wouldn't worry about it, if you have the correct pressure with the pump running you're sorted ;-)
Max_Torque said:
1st question: why do you care if fuel pressure is close to (or at zero) when the engine is not running?
2nd question: Why do you think that your regulator would be able to "hold" pressure at zero flow?? (most regs i have ever taken apart just use a metal on metal seat (for durability) so it isn't a perfect seal, and hence doesn't hold pressure with the pump off.
3rd question: the non return valve in HP pumps is generally just a ball bearing type, again, unlikely to be able to hold a "zero leak" pressure head.
I wouldn't worry about it, if you have the correct pressure with the pump running you're sorted ;-)
To be honest MT I wasn't that worried but reading the above thought that having some pressure was good after the initial prime 2nd question: Why do you think that your regulator would be able to "hold" pressure at zero flow?? (most regs i have ever taken apart just use a metal on metal seat (for durability) so it isn't a perfect seal, and hence doesn't hold pressure with the pump off.
3rd question: the non return valve in HP pumps is generally just a ball bearing type, again, unlikely to be able to hold a "zero leak" pressure head.
I wouldn't worry about it, if you have the correct pressure with the pump running you're sorted ;-)
So I guess that I'll be taking it off then????
Graham
Well, it worked...nicely!
With the non-return valve in place on the 'return' from the POT to the tank, the LP pump working like a dream again with a non-return just after to the POT, my baby burst into life this weekend without a hiccup, and idled nicely until up to temp....
...I did have one heart-stopping moment though... on the first trial, the engine ran for a bit, then got a little lumpy... I was faffing around the front of the car for a full 2 mons before I noticed a puddle growing under the rear of the car...
excess coolant I thougt... until I stuck my finger in the puddle, and smelled...fuel
Off with the ign, disconnect the battery...copious amounts of sand...leaping around like a cat on a hot tin roof, I mopped everything up I could find...
all doors open... thankfully a strong breeze I waited for a while...
I had a good look around and found both the feed and return pipe nuts to the reg loose! I MUST be getting senile! I could swear I tightened these up... Jeez!
It was only later it dawned on me that me and my project might have had a very short trip to 'never-never' land!
Later...much later...second run was uneventful...but the changes to the fueling worked...and the reg pressure only slowly reduced after initial power-on as before.
With the non-return valve in place on the 'return' from the POT to the tank, the LP pump working like a dream again with a non-return just after to the POT, my baby burst into life this weekend without a hiccup, and idled nicely until up to temp....
...I did have one heart-stopping moment though... on the first trial, the engine ran for a bit, then got a little lumpy... I was faffing around the front of the car for a full 2 mons before I noticed a puddle growing under the rear of the car...
excess coolant I thougt... until I stuck my finger in the puddle, and smelled...fuel
Off with the ign, disconnect the battery...copious amounts of sand...leaping around like a cat on a hot tin roof, I mopped everything up I could find...
all doors open... thankfully a strong breeze I waited for a while...
I had a good look around and found both the feed and return pipe nuts to the reg loose! I MUST be getting senile! I could swear I tightened these up... Jeez!
It was only later it dawned on me that me and my project might have had a very short trip to 'never-never' land!
Later...much later...second run was uneventful...but the changes to the fueling worked...and the reg pressure only slowly reduced after initial power-on as before.
Edited by V8 Vum on Monday 5th September 09:04
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