Fuel pressure gauge and pressure

[wil440]

Just finished fitting a Isspro  mechanical fuel pressure gauge, this took 1 1/2hrs, removed the factory ash tray and the two top small bolts/screws behind were the same width apart as a cheap gauge mount I had so easy mounting and away from the pillar which I want to keep free for 3 other gauges I also slipped some Cat fuel line hose over the small plastic line for added protection in the engine bay and under the dash all the way from gauge to FP, still got to Zip Tie it all up but had to run it to check for leaks.

FP sits at 15 to 16psi at idle, I haven't driven it yet as it's behind my work van, to swap them around my work van has to go onto the road  for a minute or two so seeing as I'd had well over a UK gallon of American IPA in a craft pub last night  I'll do that tomorrow.

I did a torque stall and FP drops to 7 or 8 psi, now I think thats too low but last week when towing 9k + I did check temps of the VP and it was what I'd call warm but no where near hot. In hindsight I should have checked the tank temps and I had a DMM that has a laser temp deal on it with me DOH

 

I think I have two options here.

1. Truck has a Fass stock replacement that is in the stock position with stock lines, I could 1/2" line kit it and relocate LP to the frame next to the tank and it be not much better

OR

2. DTT Assassin which removes the LPFP from the ECM and adds reliability, this kit from DAP comes with a big line kit and draw straw

 

I am leaning towards a mechanical LPFP anyway but I'd want to be looking at the whole fuel system to figure out how to get more fuel going back to tank whilst keeping good FP and also route this through fuel coolers IF the tank was getting warm, I have a Cat fuel filter complete on the truck and I can't remember if any fuel returns go back to FF housing or tank or both but intend checking tomorrow, It's too hot here at the moment, my garden temp sensor say 44C in full sun... mad dogs might but this Englishman won't

The only downside of option 2 I can see is It hangs off of the front of the engine low down so deep water/mud etc might be a problem but then again here in the uk would I be offroading a 21 year old truck made in another country thats the size of a small house and at best parts take a while to get here.... most likely not

 

Is anyone using a DTT ???

[01cummins4ever]

No experience with the DDT mechanical, but I run the FuelBoss Mechanical, pretty much same set up, as far as the crank mounting location it will not give you any issues and is fairly protected by the radiator and other crossmembers and such, You might try looking at the Glasier Diesel Power web site for the fuel boss and compare to the ddt. The Mechanical creates a lot of pressure and will keep your VP happy with a consistent 16 to 18 psi at idle and WOT. All extra fuel is sent back to the tank via a regulated bypass valve. 

[Bullet]

5 hours ago, wil440 said:

Just finished fitting a Isspro  mechanical fuel pressure gauge, this took 1 1/2hrs, removed the factory ash tray and the two top small bolts/screws behind were the same width apart as a cheap gauge mount I had so easy mounting and away from the pillar which I want to keep free for 3 other gauges I also slipped some Cat fuel line hose over the small plastic line for added protection in the engine bay and under the dash all the way from gauge to FP, still got to Zip Tie it all up but had to run it to check for leaks.

FP sits at 15 to 16psi at idle, I haven't driven it yet as it's behind my work van, to swap them around my work van has to go onto the road  for a minute or two so seeing as I'd had well over a UK gallon of American IPA in a craft pub last night  I'll do that tomorrow.

I did a torque stall and FP drops to 7 or 8 psi, now I think thats too low but last week when towing 9k + I did check temps of the VP and it was what I'd call warm but no where near hot. In hindsight I should have checked the tank temps and I had a DMM that has a laser temp deal on it with me DOH

 

I think I have two options here.

1. Truck has a Fass stock replacement that is in the stock position with stock lines, I could 1/2" line kit it and relocate LP to the frame next to the tank and it be not much better

OR

2. DTT Assassin which removes the LPFP from the ECM and adds reliability, this kit from DAP comes with a big line kit and draw straw

 

I am leaning towards a mechanical LPFP anyway but I'd want to be looking at the whole fuel system to figure out how to get more fuel going back to tank whilst keeping good FP and also route this through fuel coolers IF the tank was getting warm, I have a Cat fuel filter complete on the truck and I can't remember if any fuel returns go back to FF housing or tank or both but intend checking tomorrow, It's too hot here at the moment, my garden temp sensor say 44C in full sun... mad dogs might but this Englishman won't

The only downside of option 2 I can see is It hangs off of the front of the engine low down so deep water/mud etc might be a problem but then again here in the uk would I be offroading a 21 year old truck made in another country thats the size of a small house and at best parts take a while to get here.... most likely not

 

Is anyone using a DTT ???

I'm using a Fuel boss which is very similar to the DTT Assassin but not exactly the same...both are mechanical belt driven off the crank and mount in the exact same spot.  The mechanical pump has been extremely reliable...I haven't given fuel pressure a second thought since install.  Pressure is 18 idle and 20 when I gas it.  The best thing about a mechanical is the dynamic fueling...pumps more pressure at higher rpms.  All electrics are static so they pump less pressure at higher rpms.  Reliability is the next best thing.  All electrics have an expiration date...I don't care what name brand it is.  The last best thing is customer service...Richard at Glacier Diesel was great to work with. 

 

I don't have personal experience with the DTT Assassin...but I can recommend the Fuel Boss. 

Edited August 25, 2019 by Bullet

[dripley]

No experience here with either mechanical pumps but plenty with a gallon of most any beer, UK or USA. Either will tend to delay or slow down a repair. Keep a stiff upper my friend.

Edited August 25, 2019 by dripley

[SilverMoose]

10 hours ago, wil440 said:

Truck has a Fass stock replacement that is in the stock position with stock lines, I could 1/2" line kit it and relocate LP to the frame next to the tank and it be not much better

Just to let you know, I just added a 1/2" big line out to my FASS ddrp and relocated it just in front of the tank.  One thing you can do is remove the aluminum plate and stretch the spring just a little bit ( no more than 3mm). With my stock setup, idle is 19 psi and it WOT is 15 psi.

 

L8tr

D

[IBMobile]

Fuel Boss mounted.  You would have to rip the bumper off to hit the fuel pump.

 

                       

[Bullet]

Just now, IBMobile said:

Fuel Boss mounted.  You would have to rip the bumper off to hit the fuel pump.

 

                       

Exactly...if you hit something high enough to take out the Fuel Boss then you'll have bigger problems to worry about.  

[Mopar1973Man]

Might be true. Tall grass get wound up in the belt. Driving through thick mud or snow. I'm would be concerned with loose object that might be possible to trip the belt off the pulleys or break the belt. 

 

Major mudslide happed up here no long ago where mud cover the highway. Fiddle Creek, Idaho

 



 

Edited August 26, 2019 by Mopar1973Man

[wil440]

Drove it yesterday and idle has settled to 17/18 and wot is 10 so I suppose relocating it to the frame and going 1/2" lines would sort it out but it's still an electric pump which will fail at some point and here thats not good.  At those pressures it looks as though its not as urgent as it could be so time to think which way to go assassin or boss. I like the assassin due to it having everything from tank to VP but the killer as always is import tax

On 8/25/2019 at 10:07 PM, dripley said:

No experience here with either mechanical pumps but plenty with a gallon of most any beer, UK or USA. Either will tend to delay or slow down a repair. Keep a stiff upper my friend.

Was our last public holiday here till christmas would have been rude not to try a few... problem started after mixing apa with 7.5% cider this was saturday afternoon...  sunday was a waste of time took till 4 oclock before I could see singular 

[WesHawkins]

On 8/26/2019 at 6:23 AM, Mopar1973Man said:

Might be true. Tall grass get wound up in the belt. Driving through thick mud or snow. I'm would be concerned with loose object that might be possible to trip the belt off the pulleys or break the belt. 

 

Major mudslide happed up here no long ago where mud cover the highway. Fiddle Creek, Idaho

 



 

  That up 95 from New Meadows isn’t it.  Must be getting rain up there.

[wil440]

400 mile today, fuel pressure went down to 7psi around 6 times depending on load   first good run with a gauge, mostly stayed around 10 to 15

I've got to use it tomorrow to do about 170 miles but it will be very steady and me watching the gauge then it's parked until I get the  lift pump sorted out...

[Irie808]

Wil440, have you been inside the fuel tank recently? I ask because of what i found inside my tank when changing the in-tank pump out. Tons of fine rust enveloping the screens in there. I'd want to see inside the tank just to see whats going on in there if you haven't yet

I'm a noob here but your pressures don't seem too far off from ideal from my understanding. I wouldn't be so worried if you hit 7psi a couple times when people say that 8psi WOT is considered good.

 

[wil440]

40 minutes ago, Irie808 said:

Wil440, have you been inside the fuel tank recently? I ask because of what i found inside my tank when changing the in-tank pump out. Tons of fine rust enveloping the screens in there. I'd want to see inside the tank just to see whats going on in there if you haven't yet

I'm a noob here but your pressures don't seem too far off from ideal from my understanding. I wouldn't be so worried if you hit 7psi a couple times when people say that 8psi WOT is considered good.

 

I've never been in the tank yet,  but I'd like to see 20psi wot as being in the uk I can't deal with a vp thats quit miles from home while towing my trailer, recovery companies here wouldn't manage it so I'm paranoid and a VP to me would be 2 weeks to a month to my door.

I could just big line the fass stock mount pump it has but it is still electric, pretty sure I'm just going to put a DTT on it, I say DTT as Dap has that pump and it's a complete kit front to back and they just sent me the gauge kit which took just 2 days to me for a reasonable shipping cost

[Irie808]

I assume installing the mechanical fuel pump with the big line kit would lead you to getting inside the tank to do the draw straw. Would it be possible to install all the lines needed for your DTT prior to the pump install itself? I imagine the big line kit for the DTT would be specific to that pump and maybe not able to use on the stock setup you have now. Just a thought, might help you break up the cost and labor time into 2 parts. Would be interesting to see what difference the big line kit makes with the setup you have now.

 

SilverMoose seems to have good results with the pump you have and the big line kit.

[dripley]

I would have to say that 5 to 7 psi at WOT is not satisfactory unless maybe a stock set up. Especially if you were seeing better shortly before. Could be the screens are clogging or the filter. There are different schools of thought on pressure, me personally, I dont want to see less than 14 psi at WOT. The lower pressres could the cause of the bucking @wil440 has been experiencing. 

[Bullet]

The way I look fuel pressure...it takes 14psi to open up the overflow back to the tank which means that the VP is full of fuel.  Since fuel lubricates and cools the VP then having the overflow open means that you are doing the absolute maximum amount of cooling and lubricating.  Not having the overflow open means you are doing less than the maximum.  So the ultimate goal is to have the overflow open at all times...which means no less than 14psi at all times.  Anything less could adversely affect the longevity of the VP. 

Edited August 30, 2019 by Bullet

[wil440]

10 hours ago, Irie808 said:

I assume installing the mechanical fuel pump with the big line kit would lead you to getting inside the tank to do the draw straw. Would it be possible to install all the lines needed for your DTT prior to the pump install itself? I imagine the big line kit for the DTT would be specific to that pump and maybe not able to use on the stock setup you have now. Just a thought, might help you break up the cost and labor time into 2 parts. Would be interesting to see what difference the big line kit makes with the setup you have now.

 

SilverMoose seems to have good results with the pump you have and the big line kit.

I agree it would be interesting to relocate what I have (been on the to do list for ages) and I'm sure it would then put the FP where it needs to be but it is still electric and one day will fail

The cost of say a DTT is reasonable it's just the total when it gets here that hurts

6 hours ago, dripley said:

I would have to say that 5 to 7 psi at WOT is not satisfactory unless maybe a stock set up. Especially if you were seeing better shortly before. Could be the screens are clogging or the filter. There are different schools of thought on pressure, me personally, I dont want to see less than 14 psi at WOT. The lower pressres could the cause of the bucking @wil440 has been experiencing. 

Yes 5 to 7 wasn't nice to see, it was 15 to 18 on the drive idling but that wasn't hot, it's sitting at 12 to 14 idling hot

And yes it could be FP causing the engine off/on problem but it's that fast I never got to check the gauge as it isn't regular and I can't replicate it just happens

4 hours ago, Bullet said:

The way I look fuel pressure...it takes 14psi to open up the overflow back to the tank which means that the VP is full of fuel.  Since fuel lubricates and cools the VP then having the overflow open means that you are doing the absolute maximum amount of cooling and lubricating.  Not having the overflow open means you are doing less than the maximum.  So the ultimate goal is to have the overflow open at all times...which means no less than 14psi at all times.  Anything less could adversely affect the longevity of the VP. 

I have to use it today but It will be very steady drive to take a look at a 5th wheel then it is in pieces to be fixed once and for all

[KATOOM]

I dont have experience with a mechanical fuel pump system but I understand the Fuel Boss is a superior setup.  Any electric fuel pump isnt going to reduce reliability as long as a relay is utilized in the wiring to remove amperage draw.

 

But I have to ask...are you running fuel into the cab?  If so then I highly suggest you convert your fuel pressure gauge fitting and pressure line to a JIC type and get rid of the compression plastic line.  I eliminated the isolator years ago because it would never work right and always caused pressure reading problems, and leaked too.

[Irie808]

On 8/29/2019 at 5:51 PM, Bullet said:

The way I look fuel pressure...it takes 14psi to open up the overflow back to the tank which means that the VP is full of fuel.  Since fuel lubricates and cools the VP then having the overflow open means that you are doing the absolute maximum amount of cooling and lubricating.  Not having the overflow open means you are doing less than the maximum.  So the ultimate goal is to have the overflow open at all times...which means no less than 14psi at all times.  Anything less could adversely affect the longevity of the VP. 

 

Thanks for clarifying this, my bad As I said still a noob here. You all rock!

[wil440]

3 hours ago, KATOOM said:

But I have to ask...are you running fuel into the cab?  If so then I highly suggest you convert your fuel pressure gauge fitting and pressure line to a JIC type and get rid of the compression plastic line.  I eliminated the isolator years ago because it would never work right and always caused pressure reading problems, and leaked too.

temporarily yes, I'd rather see what my fp is than be too worried about 15 psi of diesel in the cab, and I sheathed the pipe in fuel line and sealed both ends to the fittings to make sure it it doesn't  rub through, I work on heavy diesels all day and believe me the worst place for a leak is engine side not in the cab as about the only thing hot enough to ignite diesel is exhaust manifold and turbo.

Truck is parked now anyway as I'm ripping it all off and doing it once and for all