Engine/Transmission (1994 - 1998) Lift pump on a 12 valve??

[Morse]

This is going to show how little I actually know about these trucks, though here it goes. . The 95 12 valve in the signature was just recently started for the first time since the transformation from stock. . It hasn't even been driven yet. . On the duramax and I see new cummins trucks, we use inline lift pumps to keep pressure up. . Do I need this for the 12 valve as well. . I know the pump is mechanical, though would it benefit from an inline pump?? Thanks...

 

[Joe G.]

The stock 12 valve lift pump is almost bullet proof. Extremely reliable gadget. Moves a lot of fuel.

 

[budctdca]

Well, with what has been done according to your signature, you should have a plethora of gauges to monitor all of it. If you have a fuel pressure gauge i would recommend watching what happens to fuel pressure, if it dips below what is needed (I don't have the #'s), an auxillary pump may be necessary. I know a few guys that build sled trucks and they often run an extra pump to help move the fuel. I do agree with JoeG. in that the stock one can move alot of fuel and is extremely reliable, since it is not like the new ones.

 

[PKemp]

JoeG is absolutely right. The mechanical pump is almost bullet-proof. You would need outrageous mods to require a "pusher" pump.

But... ... . The P7100 pump really likes a constant fuel pressure that doesn't "pulse" and can't be drawn down. I have replaced the under-hood fuel filter, heater and mechanical pump with a FASS fuel system. The engine is remarkably quieter, response to the pedal is notably better and quicker, the engine is smoother (used to shudder between 1300 and 1600 rpms - thats gone) and fuel mileage is up 1. 3mpg. The fuel filter and water separator are on the new pump frame and are easy to replace/change. The diameter of the fuel supply line (comes with pump) is larger, so more available volume as well as a constant pressure and you get rid of all those nasty fuel lines that are hard to replace behind the injector pump and fuel filter (old ones). The FASS also comes with an incredible warranty and the new pump is even rebuildable.

I for one am satisfied with the purchase. Installation is not difficult, simple hand tools and a drill. Very good directions/instructions come with the kit. A few friends thought I put a 24 valve in the truck its so quiet. The 12 valve, valve clatter is still apparant but the pump noise is all gone... .

For more info and ideas call Mark at Piers Diesel Research. Don't email him, he takes for ever to answer (sorry Mark).....

 

[Joe G.]

I'm wondering if a pressure regulator would have the same affect without the cost.

 

[Morse]

Thanks guys. .

 

[PKemp]

The regulator would have to have a reservoir to sustain a constant volume without the pulse. It could then be adjustable and have a port for a pressure gauge... ... hmmmmmm...

 

[Vaughn MacKenzie]

PKemp I've been wanting to talk to a 12v guy with a FASS! PM sent

Vaughn

 

[bmoeller]

The regulator would have to have a reservoir to sustain a constant volume without the pulse. It could then be adjustable and have a port for a pressure gauge... ... hmmmmmm...

There is such a thing. It is called an accumulator. Hydraulic systems use them to cushion the system from pressure spikes.



One part of it is charged with nitrogen or some other gas.

 

[Vaughn MacKenzie]

An accumulator. . . that's a thought. I did some looking and found a Bosch one found on Porsche and Mercedes fuel systems. Problem is they're over $100 and the fuel fittings look kinda smallish.



I see Cummins has an accumulator on their injection system of the common rail 8. 3: http://www.cummins.com/eu/pages/en/products/bus/engines/isce/index.cfm

 

[RonA]

My FASS went out recently. I wondered how long it would last supplying fuel to my p7100. 18 months and 21k miles is how long it lasted at 24lbs fuel pressure. I am installing a 12 valve lift pump.

 

[bmoeller]

I see Cummins has an accumulator on their injection system of the common rail 8. 3: http://www.cummins.com/eu/pages/en/products/bus/engines/isce/index.cfm

I beleive that is part of the fuel injection pump, not a seperate compoent. Not 100% sure, though.

 

[bmoeller]

My FASS went out recently. I wondered how long it would last supplying fuel to my p7100. 18 months and 21k miles is how long it lasted at 24lbs fuel pressure. I am installing a 12 valve lift pump.

Would a RASP be better than a FASS? It is mechanically operated, not electric. Belt driven, I think.

 

[Joe G.]

Basically there is nothing wrong with the stock lift pump. I get good mileage (20 on the road) and as much power as I want. It runs good. Starts instantly. As far as the pump liking a constant pressure without the spikes, it sure runs a long time in spite of the dislike.

 

[Animal]

=Vaughn MacKenzie]An accumulator. . . that's a thought. I did some looking and found a Bosch one found on Porsche and Mercedes fuel systems. Problem is they're over $100 and the fuel fittings look kinda smallish.

Here you go; http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7979663269&category=33553

 

[Joseph Donnelly]

Sickly got 800 hp with the stock lift pump.

 

[JohnG]

Fuel pressure

I finally got my guages hooked up, incl a 50 psi fuel press. But when I picked up the truck, the guy said I prob need a lift pump as the fuel pres is at 10 psi. When I started it it was down to 8. Now after driving about 20 miles, it's down to 2 psi !! BUT still runs like it did before. . !?! No stumbling or roughness. . (They also changed the fuel filter and adj the valves in the same session). . What's going on?. . Bad guage? There are some tiny bubbles in the line between the isolator and the guage, but they were there also when I first got in (at 8 psi). JohnG

 

[Joe G.]

Where is the gauge connected to the fuel system?

 

[J.R. Adkins]

Brad I use a electric pusher. It works well.





J. R.

 

[JohnG]

fuel pres

My fuel pres guage is connected at the top of the fuel filter. . And I'm beginning to think these guys might be trying to sell me the most expensive part first. . (Lift pump), (disappointing), because on speaking with one of the more sharp guys at this shop. . (The P7100 specialist), he said that the FIRST thing they check is the overflow valve, yet that was not the first thing out of the 'shop formans' mouth. He came right off with. . "you prob need a lift pump". . On asking the pump wizard, he told me, to my surprise, that the engine WOULD run, prob pretty well, even with the lift pump pushing 0 psi. . !! , but that a more likely prob was the overflow valve. . (I thought eng would be just dead w/ 2 psi at the guage. ). Anyhow, I'm not sure I'm having a great deal of faith in this shop. Shop foreman told me he's never even put a #10 plate in a '95. . They have ALWAYS put nothing but #8 or #6 in with no probs. . so I agreed with putting in a #6 AND 3000 GSK at the same time. . (we'll see what happens there in a day or so). . He also said he's never seen fuel lines go bad in a truck of my vintage. . ? Makes me wonder if my reading here in TDR is remotely connected to the 'real' world'. . OR if these guys are in a small universe. . Everytime I try to mention something about probs I've read about in TDR, they've looked at me like I was from mars. . fuel lines?? overflow valves. . ?? star wheel?? afc springs ??, yet they have a wonderful looking shop with all kinds of magnificent looking diesel pump testing equip. . Maybe I am from Mars. . ?