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JAG1

Fuel Pressure Gauge needed on 12 Valves too

14 posts in this topic

In trying to find why my old 1992 truck idles terrible after an injector and VE pump change (runs good otherwise), I've been checking for air leaks/ fuel leaks/ timing etc., I decided to replace the lift pump and delete the fuel heater since they looked like they were weeping fuel.

 

I found when I took off the old lift pump the linkage that pulls down the diaphragm was no longer connected to the actuating arm that rides on the cam. This means I drove around for about a week with a new VE injection pump and no fuel pressure :mad:. This was odd since most mechanical pumps fail from a worn leaking diaphragm, not a cheaply pressed in linkage inside. In looking at the original L/P from 1992, it was built much better and had twice the miles on it and still worked. So off I went looking at new L/Pumps,but all were from Korea or Turkey and all had the same cheaply built insides as the one that failed. I went to Cummins parts an found they even sell this new cheaply built version as well but theirs did not say where it is made:mad:.

 

This is the moment I learned  even the old 12 valves need to have a fuel pressure gauge as well.

 

I'm installing it with no Isolator, but, will have two lines going to the gauge so if leak develops the outer line will capture the leak and let it drain in the engine area. Not sure about all the ways yet but figuring it out.

Suggestions very welcome, thanks.

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Just ignore if my ignorance is showing. But couldn't you just run a GDP fuel boss for the lift pump. All mechanical, belt driven. And I am not sure other than I love the idea of all mechanical analog gauges, why not just do like the rest and go electronic? 

 

Side note a cowl mounted FP gauge would be kinda cool and eliminate the fuel in the cab worry. 

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I think I can do the outer sheath so it drains any leaks outside. After I install the plastic tube line to the gauge, slide a larger outer tube over the feed tubing and attach with permatex and clamp over the brass gauge connection nipple at the top.. I think that will work cause having a gauge outside exposed to the elements may not be good. Gauge has a plastic PVC housing that probably won't like UV rays.

 

 I  think Michael Nelson said the P.S.I. should be between 6 and 12 in a VE injection system. Did I get that right?

 

Many thanks Josen.

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You still need a needle valve inline... Works as a shutoff in case of a leak, and more importantly, a snubber to dampen injection pump pulses.

 

Bosch specs are 3-10 PSI. Stock diaphragm pumps will put out no more than 6 PSI, maybe 7 with no load and high RPM.

 

Have you looked into the Cummins piston pumps? I have the Hungry Diesel's piston pump kit, which can also be had cheaper if you source the parts individually.

Those pumps are still made in China, but there's been hardly any problems reported, with thousands being used.

 

I'm running about 16 PSI with my pump. I can pull it down to 5ish on a WOT run with big honkin injectors.

 

And @Jolsen, personally l don't see any reason for doing a fuel boss on a 12 valve, considering they use a fully mechanical block mounted pump, driven by the cam.

 

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Posted (edited)

Yes, I put on a needle valve.

 

Main reason for the gauge on a mechanical pump engine is because of the cheaply made  mechanical pump now, not like the original, mine failed involving the linkage coming apart.... used to be the diaphragm would always go.

 

Thank you for the tip on Cummins piston pumps. Like it when I get a new item to read about.

 

I'm getting average 6 p.s.i ,can pull down to around 4 if I really get on it but glad I did not do that much as my Turbo was leaking oil into the intercooler and didn't know it.

Sometimes I see 7.5 p.s.i. but rarely.

Edited by JAG1

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I never liked the diaphragm pumps design a whole lot, I've had multiples fail (non-Cummins).  One the linkage broke, fell apart, and because it was mounted to the injector pump, the whole governor housing was full of metal for it to chew on.  Had to take the injection pump off and get it rebuilt. 

 

I would agree with Texas CTD, the piston pump is a viable option, you should be able to get a good 300k miles out of it like the P-Pump 12 valve guys do.  The low pressure piston pump is a cummins variant to the one on P-pump engines, just with smaller bore, and weaker spring, otherwise they're basically identical, so you should be able to expect the same life span.

 

Jolsen

Electric pumps are great upgrade and all, but their 5 times the cost, and have half the expected life cycle.  So unless you need the extra fuel the electric pumps are capable of, then there isn't much point in it.  The Fuel Boss is a fix for reliability issues of electric fuel pumps, so if you're using a block mounted mechanical, there isn't much point in it either. 

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Posted (edited)

They put a weaker spring in so it doesn't make as much pressure. as the pump actually 'pumps' on the return stroke.

Edited by Cowboy

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4 hours ago, Mopar1973Man said:

What about the pressure limitations of the VE pumps? Wouldn't piston pump be too much pressure? 

The Hungry Diesel offers 12 PSI and 15 PSI pumps. And of course you can play with springs yourself to get desired pressure.

 

Mine runs 16 PSI. No problems, and none of Eric's customers report problems with that much pressure.

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On 3/7/2017 at 5:40 PM, Mopar1973Man said:

What about the pressure limitations of the VE pumps? Wouldn't piston pump be too much pressure? 

 

Potentially. Wil push the seal out if too much pressure is introduced. Most I have seen loctite and stake the seal in.

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On 3/9/2017 at 8:00 AM, jlbayes said:

 

Potentially. Wil push the seal out if too much pressure is introduced. Most I have seen loctite and stake the seal in.

Interesting solution... Is it a solid solution though?

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14 hours ago, Mopar1973Man said:

Interesting solution... Is it a solid solution though?

 

Seems to be. I generally do not hear about the seal failing afterwards.

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Yes that is what they were doing.

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