CIS System Pressure vs Primary Pressure Regulator
06-11-2021, 07:14 PM
#122
Rennlist Member
Thread Starter
just after the fuel accumulator, then it will certainly be a fuel pump issue. (No leaks at fuel accumulator)
06-14-2021, 11:55 AM
#123
Rennlist Member
Thread Starter
- at the outlet of my fuel pump : almost 2liter / 30 sec
- at the outlet of my fuel accumulator : almost 2liter/ 30 sec
Same amount of flow after fuel pump and accumulator and more than sufficient
So this would mean that my FD is the culprit since it is blocking almost 1300cc of the almost 2000cc flow!
06-14-2021, 12:40 PM
#124
Rennlist Member
Hi Gerrit, that is good news I think, well bad news for the fuel distributor…You could maybe send it to an expert to do the overhaul? Or do you want to go and try it yourself? Step by step you are getting closer to the solution 👍
06-14-2021, 04:21 PM
#125
Three Wheelin'
before diving into the FD i would do at least a test with a new fuel pump..... pumps work on a certain point of their spec , flow / pressure.
The 2000 cc with a free flowing pump doesn't tell much imho.... you want the system back pressure , and see 1130 cc according WSM .
You eliminated already most possible parts , so yes, if no good result with a new pump we can assume the FD .
The 2000 cc with a free flowing pump doesn't tell much imho.... you want the system back pressure , and see 1130 cc according WSM .
You eliminated already most possible parts , so yes, if no good result with a new pump we can assume the FD .
06-14-2021, 04:38 PM
#126
Rennlist Member
Thread Starter
before diving into the FD i would do at least a test with a new fuel pump..... pumps work on a certain point of their spec , flow / pressure.
The 2000 cc with a free flowing pump doesn't tell much imho.... you want the system back pressure , and see 1130 cc according WSM .
You eliminated already most possible parts , so yes, if no good result with a new pump we can assume the FD .
The 2000 cc with a free flowing pump doesn't tell much imho.... you want the system back pressure , and see 1130 cc according WSM .
You eliminated already most possible parts , so yes, if no good result with a new pump we can assume the FD .
What I find strange is that there is no direct indication that my FD is bad, except the fuel volume & system pressure. Rest pressure of my FD is fine.
If my pump would be old (>3 years), I would say replace it....but I hardly drove my car since about 2 years having a new original Bosch pump...nor debris coming out of pump or filter....not even at the inlet.
Tank is also clean.
But it cannot hurt replacing it. I suppose the Bosch pump is still the one I need...
06-15-2021, 03:56 AM
#127
Three Wheelin'
fuel accumulator & filter will indeed already give some minor resistance to make the pump work at a certain point of it's spec.
But you have nothing to compare.... who says a healthy pump wouldn't give in your test 3000 cc instead of the 2000 you see ?? or the 2000 cc is correct ??
But you have nothing to compare.... who says a healthy pump wouldn't give in your test 3000 cc instead of the 2000 you see ?? or the 2000 cc is correct ??
06-15-2021, 08:51 AM
#128
Rennlist Member
Thread Starter
fuel accumulator & filter will indeed already give some minor resistance to make the pump work at a certain point of it's spec.
But you have nothing to compare.... who says a healthy pump wouldn't give in your test 3000 cc instead of the 2000 you see ?? or the 2000 cc is correct ??
But you have nothing to compare.... who says a healthy pump wouldn't give in your test 3000 cc instead of the 2000 you see ?? or the 2000 cc is correct ??
I searched for specs of Bosch fuel pump but couldn’t find it. No idea if someone on this forum tested pump like this and whether same issues were detected.
Specs of Bosch pump 0580 254 053 is 228 liter / h. Or 3,8 liter / min.
So I had 1,9 liter / 30 sec, thus my pump is ok.
Last edited by GerritD; 06-15-2021 at 10:02 AM.
06-18-2021, 04:10 PM
#129
Rennlist Member
Thread Starter
fuel accumulator & filter will indeed already give some minor resistance to make the pump work at a certain point of it's spec.
But you have nothing to compare.... who says a healthy pump wouldn't give in your test 3000 cc instead of the 2000 you see ?? or the 2000 cc is correct ??
But you have nothing to compare.... who says a healthy pump wouldn't give in your test 3000 cc instead of the 2000 you see ?? or the 2000 cc is correct ??
with some resistance to see whether pump performance under a certain load.....
06-18-2021, 04:34 PM
#130
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Gerrit --
The flows you see directly from the pump are to be expected. The Real Test is from the return flow after the fuel pressure regulator, with primary pressure set correctly. That tests the pump's flow capacity at normal working pressures, looking for a number that's sufficient to supply the engine at maximum load/RPM's. The test procedure in the workshop manual is exactly that test. So while the pump free-flow test is interesting, it's not the test you are looking for.
The flows you see directly from the pump are to be expected. The Real Test is from the return flow after the fuel pressure regulator, with primary pressure set correctly. That tests the pump's flow capacity at normal working pressures, looking for a number that's sufficient to supply the engine at maximum load/RPM's. The test procedure in the workshop manual is exactly that test. So while the pump free-flow test is interesting, it's not the test you are looking for.
06-19-2021, 06:52 PM
#131
Rennlist Member
Thread Starter
Gerrit --
The flows you see directly from the pump are to be expected. The Real Test is from the return flow after the fuel pressure regulator, with primary pressure set correctly. That tests the pump's flow capacity at normal working pressures, looking for a number that's sufficient to supply the engine at maximum load/RPM's. The test procedure in the workshop manual is exactly that test. So while the pump free-flow test is interesting, it's not the test you are looking for.
The flows you see directly from the pump are to be expected. The Real Test is from the return flow after the fuel pressure regulator, with primary pressure set correctly. That tests the pump's flow capacity at normal working pressures, looking for a number that's sufficient to supply the engine at maximum load/RPM's. The test procedure in the workshop manual is exactly that test. So while the pump free-flow test is interesting, it's not the test you are looking for.
can be responsible for my flow issue ?
My rest pressure is perfect, I get 2.7bar still after 30min...but perhaps this also causes my flow to be restricted ?
I changed the O-rings of this relieve pressure valve since my system pressure was too low....but at the end it did not change anything in the system pressure. At that point I started to check my flow.... but perhaps this valve is the culprit
Last edited by GerritD; 06-19-2021 at 07:09 PM.
06-20-2021, 03:11 PM
#132
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Gerrit --
The pressure regulator controls the pressure that pump sees, by sending all fuel that doesn't go through the injectors back to the tank. The test for volume at correct primary pressure tells us what the pump can put out at that point in its "curve". The pump's ability to flow is inversely related to the pressure at which it's flowing. More "back pressure" on the pump means less flow, hence the need to have the primary pressure set correctly before testing for volume. The "rest pressure" is an indicator of how well the fuel pressure regulator is sealing with the pump not running. This is critical especially when a warm or hot restarts are needed. If the pressure in the system falls off immediately on engine stop, the fuel in the warmer sections (engine bay) will boil to vapor and make a hot restart difficult or worse. Low flow at normal primary pressure is related to pump capability, and might be related to other restrictions between the tank and the fuel pressure regulator. In cars with an in-tank fuel pump, a stalled or partially-blocked in-tank pump would limit flow. A partially-blocked filter, a pinched hose or metal line, fouled suction screen in the tank, any could cause the low-flow condition you describe. Or it could be a weak or incorrect fuel pump.
The pressure regulator controls the pressure that pump sees, by sending all fuel that doesn't go through the injectors back to the tank. The test for volume at correct primary pressure tells us what the pump can put out at that point in its "curve". The pump's ability to flow is inversely related to the pressure at which it's flowing. More "back pressure" on the pump means less flow, hence the need to have the primary pressure set correctly before testing for volume. The "rest pressure" is an indicator of how well the fuel pressure regulator is sealing with the pump not running. This is critical especially when a warm or hot restarts are needed. If the pressure in the system falls off immediately on engine stop, the fuel in the warmer sections (engine bay) will boil to vapor and make a hot restart difficult or worse. Low flow at normal primary pressure is related to pump capability, and might be related to other restrictions between the tank and the fuel pressure regulator. In cars with an in-tank fuel pump, a stalled or partially-blocked in-tank pump would limit flow. A partially-blocked filter, a pinched hose or metal line, fouled suction screen in the tank, any could cause the low-flow condition you describe. Or it could be a weak or incorrect fuel pump.
06-20-2021, 06:39 PM
#133
Rennlist Member
Thread Starter
Gerrit --
The pressure regulator controls the pressure that pump sees, by sending all fuel that doesn't go through the injectors back to the tank. The test for volume at correct primary pressure tells us what the pump can put out at that point in its "curve". The pump's ability to flow is inversely related to the pressure at which it's flowing. More "back pressure" on the pump means less flow, hence the need to have the primary pressure set correctly before testing for volume. The "rest pressure" is an indicator of how well the fuel pressure regulator is sealing with the pump not running. This is critical especially when a warm or hot restarts are needed. If the pressure in the system falls off immediately on engine stop, the fuel in the warmer sections (engine bay) will boil to vapor and make a hot restart difficult or worse. Low flow at normal primary pressure is related to pump capability, and might be related to other restrictions between the tank and the fuel pressure regulator. In cars with an in-tank fuel pump, a stalled or partially-blocked in-tank pump would limit flow. A partially-blocked filter, a pinched hose or metal line, fouled suction screen in the tank, any could cause the low-flow condition you describe. Or it could be a weak or incorrect fuel pump.
The pressure regulator controls the pressure that pump sees, by sending all fuel that doesn't go through the injectors back to the tank. The test for volume at correct primary pressure tells us what the pump can put out at that point in its "curve". The pump's ability to flow is inversely related to the pressure at which it's flowing. More "back pressure" on the pump means less flow, hence the need to have the primary pressure set correctly before testing for volume. The "rest pressure" is an indicator of how well the fuel pressure regulator is sealing with the pump not running. This is critical especially when a warm or hot restarts are needed. If the pressure in the system falls off immediately on engine stop, the fuel in the warmer sections (engine bay) will boil to vapor and make a hot restart difficult or worse. Low flow at normal primary pressure is related to pump capability, and might be related to other restrictions between the tank and the fuel pressure regulator. In cars with an in-tank fuel pump, a stalled or partially-blocked in-tank pump would limit flow. A partially-blocked filter, a pinched hose or metal line, fouled suction screen in the tank, any could cause the low-flow condition you describe. Or it could be a weak or incorrect fuel pump.
Any extra shim in the pressure regulator valve did not affect my system pressure while normally it should.
So then I replaced my O-rings of the fuel pressure regulator valve in my FD…
There was no improvement.
The only thing which was correct was the rest pressure.
So perhaps the fuel pressure regulator is not moving freely when pump is running and thus flow is partially blocked.
This could explain my flow issue by not my system pressure being too low, unless it is related to my flow as you mentioned.
06-21-2021, 03:33 PM
#134
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Gerrit --
I'd start by making sure that the pump can deliver the required pressure while dead-headed (outlet completely blocked briefly, no flow at all). Then move to making sure that it has the ability to maintain that pressure at rated flow (the WSM test...). If it makes plenty of pressure at zero flow but fails the WSM test, I'd put a gauge in the line at pump discharge (the S pipe fittings...) and compare that to the under-hood system pressure reading while performing the WSM test. If the pump discharge pressure is significantly higher than under-hood system pressure, there's a restriction in the filter, hoses or piping between the pump and the engine bay. If they are close (within 5PSI or so, guessing) and it still fails the WSM test (not enough pressure at test flow or not enough flow at test pressure), you may need to replace the pump(s). Many cars came with two pumps -- one small priming pump in the tank, feeding the main pump mounted on the tank. Inside the tank there's a suction screen on the end of the pump itself, with a short connecting hose from the pump discharge to the fitting in the bottom of the tank. If you look at the fitting at the tank outlet, the ones for in-tank pump have connections for wiring passing through. A telltale that there's a pump inside. If that pump fails or gets clogged with debris or the little connecting hose disintegrates (common with "modern" fuels here) there's a risk of it limiting suction flow to the main pump. If you do have that in-tank pump, it's worthwhile removing and inspecting it completely. Replace the short rubber connecting hose with modern plastic-lined injection tubing and proper clamps. Verify that it does in fact run and pump, maybe with some paint thinner/mineral spirits in a closed container.
I'd start by making sure that the pump can deliver the required pressure while dead-headed (outlet completely blocked briefly, no flow at all). Then move to making sure that it has the ability to maintain that pressure at rated flow (the WSM test...). If it makes plenty of pressure at zero flow but fails the WSM test, I'd put a gauge in the line at pump discharge (the S pipe fittings...) and compare that to the under-hood system pressure reading while performing the WSM test. If the pump discharge pressure is significantly higher than under-hood system pressure, there's a restriction in the filter, hoses or piping between the pump and the engine bay. If they are close (within 5PSI or so, guessing) and it still fails the WSM test (not enough pressure at test flow or not enough flow at test pressure), you may need to replace the pump(s). Many cars came with two pumps -- one small priming pump in the tank, feeding the main pump mounted on the tank. Inside the tank there's a suction screen on the end of the pump itself, with a short connecting hose from the pump discharge to the fitting in the bottom of the tank. If you look at the fitting at the tank outlet, the ones for in-tank pump have connections for wiring passing through. A telltale that there's a pump inside. If that pump fails or gets clogged with debris or the little connecting hose disintegrates (common with "modern" fuels here) there's a risk of it limiting suction flow to the main pump. If you do have that in-tank pump, it's worthwhile removing and inspecting it completely. Replace the short rubber connecting hose with modern plastic-lined injection tubing and proper clamps. Verify that it does in fact run and pump, maybe with some paint thinner/mineral spirits in a closed container.
Last edited by dr bob; 06-21-2021 at 03:35 PM.
06-21-2021, 05:08 PM
#135
Rennlist Member
Thread Starter
Gerrit --
I'd start by making sure that the pump can deliver the required pressure while dead-headed (outlet completely blocked briefly, no flow at all). Then move to making sure that it has the ability to maintain that pressure at rated flow (the WSM test...). If it makes plenty of pressure at zero flow but fails the WSM test, I'd put a gauge in the line at pump discharge (the S pipe fittings...) and compare that to the under-hood system pressure reading while performing the WSM test. If the pump discharge pressure is significantly higher than under-hood system pressure, there's a restriction in the filter, hoses or piping between the pump and the engine bay. If they are close (within 5PSI or so, guessing) and it still fails the WSM test (not enough pressure at test flow or not enough flow at test pressure), you may need to replace the pump(s). Many cars came with two pumps -- one small priming pump in the tank, feeding the main pump mounted on the tank. Inside the tank there's a suction screen on the end of the pump itself, with a short connecting hose from the pump discharge to the fitting in the bottom of the tank. If you look at the fitting at the tank outlet, the ones for in-tank pump have connections for wiring passing through. A telltale that there's a pump inside. If that pump fails or gets clogged with debris or the little connecting hose disintegrates (common with "modern" fuels here) there's a risk of it limiting suction flow to the main pump. If you do have that in-tank pump, it's worthwhile removing and inspecting it completely. Replace the short rubber connecting hose with modern plastic-lined injection tubing and proper clamps. Verify that it does in fact run and pump, maybe with some paint thinner/mineral spirits in a closed container.
I'd start by making sure that the pump can deliver the required pressure while dead-headed (outlet completely blocked briefly, no flow at all). Then move to making sure that it has the ability to maintain that pressure at rated flow (the WSM test...). If it makes plenty of pressure at zero flow but fails the WSM test, I'd put a gauge in the line at pump discharge (the S pipe fittings...) and compare that to the under-hood system pressure reading while performing the WSM test. If the pump discharge pressure is significantly higher than under-hood system pressure, there's a restriction in the filter, hoses or piping between the pump and the engine bay. If they are close (within 5PSI or so, guessing) and it still fails the WSM test (not enough pressure at test flow or not enough flow at test pressure), you may need to replace the pump(s). Many cars came with two pumps -- one small priming pump in the tank, feeding the main pump mounted on the tank. Inside the tank there's a suction screen on the end of the pump itself, with a short connecting hose from the pump discharge to the fitting in the bottom of the tank. If you look at the fitting at the tank outlet, the ones for in-tank pump have connections for wiring passing through. A telltale that there's a pump inside. If that pump fails or gets clogged with debris or the little connecting hose disintegrates (common with "modern" fuels here) there's a risk of it limiting suction flow to the main pump. If you do have that in-tank pump, it's worthwhile removing and inspecting it completely. Replace the short rubber connecting hose with modern plastic-lined injection tubing and proper clamps. Verify that it does in fact run and pump, maybe with some paint thinner/mineral spirits in a closed container.
I initialy had also a intank pump but I removed it since it did not work anymore. I replaced it with a suction screen 2 years ago.
I can already say that when I remove the little curved hose from tank to inlet pump, fuel is really pouring out of my tank at high volume and velocity.
So the suction screen in tank is not clogged at all. ( I also checked with a endoscopy camera)
As for the filter, I just bought a new one, 3 weeks ago. So this can be ruled out also.
Perhaps like you said, a good and easy test, can be : running my pump dead- headed at the tank side, and same test under the hood while measuring pressure.
If it goes to 6bar or more , I can continue the WSM test.
What do you mean with S-pipe fittings? What is meant with discharge line of the pump?