Fuel pressure gauge Whats the big deal ??

[Wasilla Rod]

After my lift pump went dead I decided it would not be a bad idea to install a pressure gauge. I OF COURSE went to the sponser links and looked over their wares only to be confused. Why all the snubbers and / or electronic sending units. Why can't you just hook up a simple pressure gauge with copper or plastic tube like we did for oil pressure every since we was kid hot rodders?? Am I missing something here?

 

[ASchwartz]

After my lift pump went dead I decided it would not be a bad idea to install a pressure gauge. I OF COURSE went to the sponser links and looked over their wares only to be confused. Why all the snubbers and / or electronic sending units. Why can't you just hook up a simple pressure gauge with copper or plastic tube like we did for oil pressure every since we was kid hot rodders?? Am I missing something here?

The standard of practice is to have an isolator if the gauge is within the cab, so as to keep diesel from entering the plush interior of your $40-$50K truck. :{

 

[RMarkey]

AKA. . price is higher. That's where you get that classic truck/ car smell partly I think, from the old oil pressure gauge in the cab. It never leaks but always has a film on it and smells ohh so good. There's no mistaking that classic car smell, can't beat it with a stick.

I miss the good old days when diesels always smelled like diesels and the smell can take you back in an instant. I miss the simple old days.

 

[steved]

After my lift pump went dead I decided it would not be a bad idea to install a pressure gauge. I OF COURSE went to the sponser links and looked over their wares only to be confused. Why all the snubbers and / or electronic sending units. Why can't you just hook up a simple pressure gauge with copper or plastic tube like we did for oil pressure every since we was kid hot rodders?? Am I missing something here?

A snubber is different from an isolator... a snubber dampens pulses in the fuel supply, the isolator prevents fuel from entering the cab if the line/guage fails. Typically a damper is used to prevent needle vibration in a mechanical guage, and the isolator is typically only used with a mechanical guage since they require running a line/hose into the cab. The snubber is typically a requirement for the 2nd gens because of backfed pressure spikes from the VP44.



On your 3rd gen, you would be fine with an electric guage/sensor. Unless you go to a mechanical guage, you won't need a snubber or isolator.

 

[BMH95]

I had a BD fuel pressure switch (led light in the cab) on mine, and it died and started leaking about about 25K miles. It would pulse and flicker under normal driving conditions, and is dripping. I'm told the CP3 does in fact have enough spikes to kill things. If you do searches on the forums, you'll find LOTS of dead FP gauge threads. My next task is to put a mechanical ISSPRO gauge in (sitting on bench now). I'm going to run an 18 inch grease gun hose off of the CP3 with a needle valve. Then, I'm going to tie that into a regular nylon oil line and run it to the gauge. We'll see how that lasts. I'm not worried about oil in the cab, it's not like gasoline.

 

[JLandry]

I miss the good old days when diesels always smelled like diesels and the smell can take you back in an instant.

There's a simple way to fix that...



Take a worn out car air freshener, soak it in diesel for a few minutes, shake it off, then hang it from the rear view mirror in your truck.



John L.

 

[RJWEST]

Cheap mech gage 18. 00, 1/8 copper firewall to gage,
Rubber from IP fuel tap to firewall.

Cut off bolt section with 'Small' Hole drilled for snubber in rubber line

#ad

 

[Ducman82]

ok, my question is how does the CP# cause spikes in the fuel line befor it? wouldint that hassen the death of the LP?

 

[steved]

ok, my question is how does the CP# cause spikes in the fuel line befor it? wouldint that hassen the death of the LP?

As the injection pump does its work, it pulses back into the feedline (spikes)...



I believe there are a lot of discussions about this in the 2nd gen forum... its typically a VP44 thing, and this is the first I've heard of it affecting a CP3...

 

[cerberusiam]

ok, my question is how does the CP# cause spikes in the fuel line befor it? wouldint that hassen the death of the LP?

It doesn't. The only pressure you see from the inlet of the CP-3 is from the lift pump.



The CP-3 has a gear pump to supply fuel to the high pressure side of the pump and a spool with check valve to control fuel delivery. If there are pressure spikes back feeding something is FUBARed big time in the pump and low pressure side. Considering the pressures generated for the rail, ANY back pressure would be seriously detrimental to the low pressure side components.



Even the VP44 does not back pressure the delivery side. The fluctuation is from the stock LP. Replace it with a constant flow pump and the spikes are gone.

 

[steved]

Even the VP44 does not back pressure the delivery side. The fluctuation is from the stock LP. Replace it with a constant flow pump and the spikes are gone.

This is contrary to a lot of what's been discussed on this site... the VP44 does induce back pressure "vibrations"... the stock lift pump in the 2nd gen is a rotary vane...



Not that I care... I run a snubber on a mechanical guage in the engine bay primarily to prevent dirt entering the system when I change guages, I run a low pressure light off the FASS.

 

[Ducman82]

maybe is the constant "on/off" of the CP3 sucking fuel from the LP that causes senders to go bad??? i have my electric sender mounted on the head for my 2 micron filter so im not worried, plenty of filter and hose for "spikes"

 

[steved]

Again, this is the first time I've heard of this being an issue with the CP3... it has been well discussed in the VP44 crowd...



Not sure the VP44 has an internal lift pump like the CP3 does... its been a long time since I've read any of those threads.

 

[Diesel Manor]

Another option is to simply use an electric FP gauge. Then you don't have to worry about the isolator or snubber thing. DiPricol has them and we stock them. They are all we offer in our dipricol kits now, becasue they work so well. The only problem is that right now 7/11/08, they're on backorder. We expect them in in a few more days. Seems everyone is out of them.

 

[cerberusiam]

maybe is the constant "on/off" of the CP3 sucking fuel from the LP that causes senders to go bad???

There is no on/off suction from the CP-3 low pressure pump. Its a gear pump that pressurizes the fuel to 180 psi for delivery to the high pressure circuit. No spikes, no back feed.



All excess fuel not used for injection is routed thru the pump for cooling and back to the tank. Same with the VP-44.



Think about it, if even 1% of 12k to 23k of pressure back fed the low pressure system at 8-10 psi or so what would happen.