Fuel Pressure Issue: Advice needed please
#1
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Thread Starter
Fuel Pressure Issue: Advice needed please
At my wit’s end here and would appreciate some input.
I have a Weistec E55 with loads of supporting mods. The car is really strong but I have a lingering Fuel Pressure issue that for a very long time now has been hampering my enjoyment of the car. Hope some of the experts here have some useful ideas and will chime in.
On the fuelling side, I’m running 2 AEM 320 lph pumps with the stock (brand spanking new) fuel sender unit, stock fuel lines, Weistec’s fuel rails (larger diameter than the stock rails) and Weistec’s 650cc injectors. I have new fuel relays, a new CPS and a new cam positioning sensor fitted.
I’m measuring fuel pressure via the DashDAQ. Although it’s not properly calibrated, I can gauge with enough certainty from the fluctuations in FP readings what’s happens to FP in different situations. So at idle, the DashDAQ will read at around 6.2 which equates to about 5.3 bar. On a WOT run, when the FP issue is not present, the DashDAQ reading will fall to a low of around 5 which equates to about 4 bar.
The issue: The issue is more likely to arise in hot weather than cold, when the tank is closer to empty than full and when I’ve been driving for longer periods than shortly after start-up.
When the issue arises, FP will drop off dramatically under hard acceleration, For e.g. on a short WOT burst, FP will quickly fall to low 3s and I’ll immediately come off the gas. I’m sure that if I stayed on the gas, FP would fall away altogether (and my rebuilt motor would go boom in the process).
If, after the issue has arisen, I cruise at moderate speeds, FP will usually hold-up but the moment I get on the throttle, it falls quickly to dangerously low levels. The issue will resolve itself if I park the car and allow it to cool for a period. The cool-off period required varies. Leaving the car overnight will always resolve the issue. Sometimes leaving it parked for an hour or two will suffice.
Heat is clearly a factor. The fuel rails are extremely hot to the touch, even after a short (5km) drive first thing in the morning. I’ve tried heat-wrapping the fuel lines but no improvement. My mate who’s trying to help with this thinks that when the issue arises, either the pumps begin to cavitate or the fuel starts percolating in the fuel rails. We have no idea why either of these scenarios would occur.
Any suggestions/input welcome, thx
I have a Weistec E55 with loads of supporting mods. The car is really strong but I have a lingering Fuel Pressure issue that for a very long time now has been hampering my enjoyment of the car. Hope some of the experts here have some useful ideas and will chime in.
On the fuelling side, I’m running 2 AEM 320 lph pumps with the stock (brand spanking new) fuel sender unit, stock fuel lines, Weistec’s fuel rails (larger diameter than the stock rails) and Weistec’s 650cc injectors. I have new fuel relays, a new CPS and a new cam positioning sensor fitted.
I’m measuring fuel pressure via the DashDAQ. Although it’s not properly calibrated, I can gauge with enough certainty from the fluctuations in FP readings what’s happens to FP in different situations. So at idle, the DashDAQ will read at around 6.2 which equates to about 5.3 bar. On a WOT run, when the FP issue is not present, the DashDAQ reading will fall to a low of around 5 which equates to about 4 bar.
The issue: The issue is more likely to arise in hot weather than cold, when the tank is closer to empty than full and when I’ve been driving for longer periods than shortly after start-up.
When the issue arises, FP will drop off dramatically under hard acceleration, For e.g. on a short WOT burst, FP will quickly fall to low 3s and I’ll immediately come off the gas. I’m sure that if I stayed on the gas, FP would fall away altogether (and my rebuilt motor would go boom in the process).
If, after the issue has arisen, I cruise at moderate speeds, FP will usually hold-up but the moment I get on the throttle, it falls quickly to dangerously low levels. The issue will resolve itself if I park the car and allow it to cool for a period. The cool-off period required varies. Leaving the car overnight will always resolve the issue. Sometimes leaving it parked for an hour or two will suffice.
Heat is clearly a factor. The fuel rails are extremely hot to the touch, even after a short (5km) drive first thing in the morning. I’ve tried heat-wrapping the fuel lines but no improvement. My mate who’s trying to help with this thinks that when the issue arises, either the pumps begin to cavitate or the fuel starts percolating in the fuel rails. We have no idea why either of these scenarios would occur.
Any suggestions/input welcome, thx
#2
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2004 E55,1969 300SEL6.3,2011 ML350 BlueTec Diesel,2005 ML400 CDI
Try some temperature sensitive tape on the rail and see what the indication is.
The SLR's have fuel coolers.
http://www.wahltempplates.com/
It may also be possible that the fuel line diameter from the tank to the engine is not sufficient for the Weistec setup.
The SLR's have fuel coolers.
http://www.wahltempplates.com/
It may also be possible that the fuel line diameter from the tank to the engine is not sufficient for the Weistec setup.
![nix](https://mbworld.org/forums/images/smilies/nixweiss.gif)
#3
Senior Member
Thread Starter
Try some temperature sensitive tape on the rail and see what the indication is.
The SLR's have fuel coolers.
http://www.wahltempplates.com/
It may also be possible that the fuel line diameter from the tank to the engine is not sufficient for the Weistec setup.![nix](https://mbworld.org/forums/images/smilies/nixweiss.gif)
The SLR's have fuel coolers.
http://www.wahltempplates.com/
It may also be possible that the fuel line diameter from the tank to the engine is not sufficient for the Weistec setup.
![nix](https://mbworld.org/forums/images/smilies/nixweiss.gif)
![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
I was considering a Fuel Cooler but canned the idea on the basis that none of the other Weistec 55s are having the issue (as far as I know) and installing a Fuel Cooler may simply mask some other underlying defect that needs to be addressed.
There are no insulators used by Weistec at the points where the fuel rail is bolted on. Is it possible that excessive heat is being transferred from the motor to the fuel rail as a result? We'd need to modify the fuel rail to accommodate
insulators and I'd rather not do so unless that is likely to solve the problem
#6
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[QUOTE=ajm55;6214160]Thanks for the suggestions. I'll look into them ![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
I was considering a Fuel Cooler but canned the idea on the basis that none of the other Weistec 55s are having the issue (as far as I know)[\QUOTE]
If no other Weistec 55s are having the same problem, then you could go back to the OEM fuel pump set up and see if you have the same problem.
![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
I was considering a Fuel Cooler but canned the idea on the basis that none of the other Weistec 55s are having the issue (as far as I know)[\QUOTE]
If no other Weistec 55s are having the same problem, then you could go back to the OEM fuel pump set up and see if you have the same problem.
#7
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#8
That depends on how the system works. The problem is not an inability to create vacuum, but rather the presence of excessive vacuum.
Granted, my experience with his comes from carbureted motorcycles, but the symptoms are identical.
Granted, my experience with his comes from carbureted motorcycles, but the symptoms are identical.
#11
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2007 E63 Amg, Heavily modified 1988 Jeep Comanche
It sounds like you either have a volume or resistance issue. Im thinking that once the vehicle is hot theres a electrical contact that has too much resistance in it cuz heat = resistance and two pumps at full bore is quite a lot of amprage. It may be that the wires just arnt capable of carrying the load of those two pumps. Maybe a relay and some heavier duty cables are in order to carry that load.
#12
Senior Member
Thread Starter
Thanks to all of you for the feedback.
We've wired the system so that the 2nd fuel pump relay is now triggered by the 1st rather than by the ECU. We have also installed an LED light on the dash which illuminates when current is going through to the 2nd relay. The LED will therefore illuminate from start-up and stay on at all times. Does the fact that the LED does not switch off when the FP issue arises negate your theory or would the LED remain on even if the issue is due to an amperage inadequacy?
[QUOTE=jcjmw;6214235]
Thanks, this is possibly my next move. We haven't done this yet as there are a number of modified E55s around these parts that are running high flow pumps with stock fuel lines and the stock sender unit without any issue.
If Hulk is correct, I'm not seeing any codes. It does, however, sometimes happen when I fill up that the auto filler will disengage every 5 liters or so. Once, after the FP issue had manifested, I did remove the petrol cap and resume driving but doing so didn't resolve the issue. Are you suggesting that vacuum build up would cause the fuel to heat up in the tank? If so, then clearly I'd have to remove the cap from outset and not only once the FP issue arises in order to test the theory
It sounds like you either have a volume or resistance issue. Im thinking that once the vehicle is hot theres a electrical contact that has too much resistance in it cuz heat = resistance and two pumps at full bore is quite a lot of amprage. It may be that the wires just arnt capable of carrying the load of those two pumps. Maybe a relay and some heavier duty cables are in order to carry that load.
[QUOTE=jcjmw;6214235]
Thanks for the suggestions.
I'll look into them![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
I was considering a Fuel Cooler but canned the idea on the basis that none of the other Weistec 55s are having the issue (as far as I know)[\QUOTE]
If no other Weistec 55s are having the same problem, then you could go back to the OEM fuel pump set up and see if you have the same problem.
I'll look into them
![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
I was considering a Fuel Cooler but canned the idea on the basis that none of the other Weistec 55s are having the issue (as far as I know)[\QUOTE]
If no other Weistec 55s are having the same problem, then you could go back to the OEM fuel pump set up and see if you have the same problem.
If Hulk is correct, I'm not seeing any codes. It does, however, sometimes happen when I fill up that the auto filler will disengage every 5 liters or so. Once, after the FP issue had manifested, I did remove the petrol cap and resume driving but doing so didn't resolve the issue. Are you suggesting that vacuum build up would cause the fuel to heat up in the tank? If so, then clearly I'd have to remove the cap from outset and not only once the FP issue arises in order to test the theory
#13
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2007 E63 Amg, Heavily modified 1988 Jeep Comanche
I dont know cuz the led really just needs a certian voltage to turn on. Just like lines need to be bigger to flow a greater amount of fuel, wires have to be a smaller gauge to move more electrons. If you need to increase the volume of your rails to make more power your going to need to fill those rails.
#14
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Thread Starter
I dont know cuz the led really just needs a certian voltage to turn on. Just like lines need to be bigger to flow a greater amount of fuel, wires have to be a smaller gauge to move more electrons. If you need to increase the volume of your rails to make more power your going to need to fill those rails.
![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
#15
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Ajm55- I experience none of the aforementioned problems at all. Since our setups are nearly identical , I could only assume that if your twin AEM pumps were replaced with a new MB pump/filter setup like I run, that yours would run the same.
I think those pumps are just making too much internal pressure prior to being recirculated internally and heating the fuel.
I think those pumps are just making too much internal pressure prior to being recirculated internally and heating the fuel.
#16
Senior Member
Thread Starter
Ajm55- I experience none of the aforementioned problems at all. Since our setups are nearly identical , I could only assume that if your twin AEM pumps were replaced with a new MB pump/filter setup like I run, that yours would run the same.
I think those pumps are just making too much internal pressure prior to being recirculated internally and heating the fuel.
I think those pumps are just making too much internal pressure prior to being recirculated internally and heating the fuel.
#17
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The problem I'm almost certain is the pumps heating the fuel, then cavitating at WOT as your friend suggested. Wrapping the lines was probably counterproductive as the heat is coming from inside the tank.
Are you sure both AEM pumps are functioning properly? Aftermarket stuff does fail at a much higher rate than OEM. Assuming that both pumps are wired, plumbed correctly and both functioning properly, that would leave the variable of input voltage. Your ECU programming is from Weistec while the other E55s running AEM pumps are running other software.
Have you compared the input voltages at the pump plug? I know that's a pain to check but I'm just tossing ideas. Perhaps Weistec increases pump voltage to a point that is beneficial on OEM pumps but problematic on larger AEM pumps.
Are you sure both AEM pumps are functioning properly? Aftermarket stuff does fail at a much higher rate than OEM. Assuming that both pumps are wired, plumbed correctly and both functioning properly, that would leave the variable of input voltage. Your ECU programming is from Weistec while the other E55s running AEM pumps are running other software.
Have you compared the input voltages at the pump plug? I know that's a pain to check but I'm just tossing ideas. Perhaps Weistec increases pump voltage to a point that is beneficial on OEM pumps but problematic on larger AEM pumps.
#18
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Thread Starter
The problem I'm almost certain is the pumps heating the fuel, then cavitating at WOT as your friend suggested. Wrapping the lines was probably counterproductive as the heat is coming from inside the tank.
Are you sure both AEM pumps are functioning properly? Aftermarket stuff does fail at a much higher rate than OEM. Assuming that both pumps are wired, plumbed correctly and both functioning properly, that would leave the variable of input voltage. Your ECU programming is from Weistec while the other E55s running AEM pumps are running other software.
Have you compared the input voltages at the pump plug? I know that's a pain to check but I'm just tossing ideas. Perhaps Weistec increases pump voltage to a point that is beneficial on OEM pumps but problematic on larger AEM pumps.
Are you sure both AEM pumps are functioning properly? Aftermarket stuff does fail at a much higher rate than OEM. Assuming that both pumps are wired, plumbed correctly and both functioning properly, that would leave the variable of input voltage. Your ECU programming is from Weistec while the other E55s running AEM pumps are running other software.
Have you compared the input voltages at the pump plug? I know that's a pain to check but I'm just tossing ideas. Perhaps Weistec increases pump voltage to a point that is beneficial on OEM pumps but problematic on larger AEM pumps.
I don't think we've checked the input voltage - I'll look into that. I'm actually running a Eurocharged tune - although I had the same issue previously when running the Weistec tune. I'll enquire from Jerry whether this could be tune-related. Thanks for the input
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#19
Super Member
Im sure I read the OEM pump vary pressure as needed.
It might be done by voltage which the aftermarket pumps might not like.
Like pressure on demand I would switch back to OEM and see what goes.
Also the pumps filters might be clogged or something restricting flow and causing them to heat up.
It might be done by voltage which the aftermarket pumps might not like.
Like pressure on demand I would switch back to OEM and see what goes.
Also the pumps filters might be clogged or something restricting flow and causing them to heat up.
#20
Senior Member
Thread Starter
Im sure I read the OEM pump vary pressure as needed.
It might be done by voltage which the aftermarket pumps might not like.
Like pressure on demand I would switch back to OEM and see what goes.
Also the pumps filters might be clogged or something restricting flow and causing them to heat up.
It might be done by voltage which the aftermarket pumps might not like.
Like pressure on demand I would switch back to OEM and see what goes.
Also the pumps filters might be clogged or something restricting flow and causing them to heat up.
#21
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Good luck to you! Keep us posted! If the problem is solved via reinstalling OEM pumps, then you at least know its something oem voltage related. Again, good luck!!!
#22
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#24
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06 E55 AMG, 13 C63 AMG
Back before I switched to the Weistec tuning I was having all kinds of trouble. I looked and searched and so on looking for a way to read fuel pressure and the best I could tell is that the E55 does not have a fuel pressure sensor and you cannot read fuel pressure from the OBD.
So, how are you able to read fuel pressure with a DashHawk??
G
So, how are you able to read fuel pressure with a DashHawk??
G
#25
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Thanks again for all your help and advice brotha ![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
Not sure how it is hooked up. All I know is that I had to get a particular sensor installed. Apparently there are some other guys on the forum who are also reading fuel pressure off the DashDAQ. Perhaps one of them can chime in with the details
![thumbs](https://mbworld.org/forums/images/smilies/thumbsup.gif)
Back before I switched to the Weistec tuning I was having all kinds of trouble. I looked and searched and so on looking for a way to read fuel pressure and the best I could tell is that the E55 does not have a fuel pressure sensor and you cannot read fuel pressure from the OBD.
So, how are you able to read fuel pressure with a DashHawk??
G
So, how are you able to read fuel pressure with a DashHawk??
G