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Discussion Starter #1 (Edited)
Lift pump pressure spikes after shutdown

This adventure started out looking for the air leak that has reappeared. (The lift was replaced July of 2017) After setting for a few days the IP would lose prime, no start, but pumping the arm on the lift pump a few time and it would start with out bleeding. Trying to read the small fuel pressure gauge was not working, so bought a sensor extension and moved the gauge to where I could read read.
Now i find I have good pressure at cold idle (8 psi) and a small bit of throttle it would climb to 12 psi and just after shut down the psi would climp past 15 psi, wrap the needle all the way around and then slowly drop to zero psi. This can't be normal!

My guess is the IP (VE) if feeding the pressure back to the top of the lift pump. But why, how?
Ideas, suggestions?

heres a video of it acting up:
[VIDEO]4bt lift pump
 

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Is you pressure reading coming prior to the filter or after it? Can't imagine what caused that pressure surge when you shut it down. Would have to suspect an air leak to be losing partial prime. Is there a check valve in the line to prevent bleed back?
 

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Discussion Starter #3 (Edited)
Is you pressure reading coming prior to the filter or after it? Can't imagine what caused that pressure surge when you shut it down. Would have to suspect an air leak to be losing partial prime. Is there a check valve in the line to prevent bleed back?
The gauge is taped into the banjo bolt before the filter. Also have a snubber inline too. This is all temporary.
As far as a check valve don't know, haven't found one yet from the VE pump cutaways.
correction: There is a pressure control valve just after the fuel inlet into the IP that appears that it might have a check valve in it.
 

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Discussion Starter #5 (Edited)
You still have the diaphragm lift pump? My diaphragm lift pump will not produce more than 5psi under any scenario.Seems like the regulator between the low pressure and high pressure sections of the case has gone bad, maybe stuck wide open. Sounds like it's time to rebuild your injection pump.http://www.dieselmotors.info/fuel-systems/diesel-engine-bosch-ve-fuel-pump.html
Yes have a diaphragm lift pump. I suspect the pressure control valve too. But nobody can recall ever testing for this pressure spike phenomena. Now I need someone else or two to do the same test.

edit: The IP was rebuilt in 2012.
 

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I've recently installed an electronic pressure gauge in the same place you have. On startup, I get ~5psi, WOT drops down to 0.5psi or less at higher load. On shutdown (power still applied to gauge) pressure stays consistent, and definitely does not rise up. I don't know how long it takes the pressure to drop off, but it 100% does not rise up like you're experiencing.
 

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Discussion Starter #7
I've recently installed an electronic pressure gauge in the same place you have. On startup, I get ~5psi, WOT drops down to 0.5psi or less at higher load. On shutdown (power still applied to gauge) pressure stays consistent, and definitely does not rise up. I don't know how long it takes the pressure to drop off, but it 100% does not rise up like you're experiencing.
Thanks, thats the test I was waiting for, but the results says I've something else to think about.
Are you using the FSS (fuel shutoff solenoid) or a cable pull on the emergency stop?
 

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Also run an electronic (Auberins) gauge, idling at 5 psi and shutoff and no pressure increase. FSS in use.
Cheers Steve
 

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I thought you had the piston lift pump. 15 PSI on one of those pre filter is correct. Never seen a VE diaphragm pump anywhere near that level.
 

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Just a thought, have you checked the return line banjo bolt orifice? That could give you high readings but would expect possible other damage to result as well.
Don't pass the possibility the gauge is not accurate. Currently waiting for a new VDO boost gauge as the last one I purchased is reading 5psi low then goes high after 20 psi.
Cheers Steve
 

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Discussion Starter #11
The temporary gauge is a inexpensive one less than $20 USD, it could be that inaccurate. For Christmas I gave the Scout a set of 4 GlowShift/MaxTow gauges which includes a fuel pressure gauge. Was waiting for a good time (warmer) to do the install.

Return line at the banjo bolt, will have to check that.

Have another pressure gauge, will install that one and compare readings.
thanks guys.
 

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The temporary gauge is a inexpensive one less than $20 USD, it could be that inaccurate. For Christmas I gave the Scout a set of 4 GlowShift/MaxTow gauges which includes a fuel pressure gauge. Was waiting for a good time (warmer) to do the install.

Return line at the banjo bolt, will have to check that.

Have another pressure gauge, will install that one and compare readings.
thanks guys.
That Glow Shift gauges is are going to bite ya. Sorry to say but they are regarded by many as pure junk. Just one of many I have seen over the years by word of mouth or on the forums https://www.dieseltruckresource.com/forums/performance-accessories-2nd-gen-only-91/glow-shift-gauges-328745/

I actually have a pre-written up statement for customers that contact me if they find different fuel readings other than +/- 1 psi out of my 14psi HVLP (high volume low pressure) piston kits....One of my 1st lines are
"Let me guess, you have a Glow Shift fuel pressure gauge".
 

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Yes Mark, the old saying of you get what you pay for pretty much fits gauges. For some reason I seem to prefer the pure mechanical gauges, but some have issue of running oil and fuel lines inside the cab. One company I found was Hewitt Industries and most of their gauges are pure mechanical. About the only thing they didn't have were tachs and speedometers. Cummins even offered a mechanical tach drive for these engines.
 

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A buddy of mine that has a diesel shop at first thought it was great to become a Glow Shift dealer until customer after customer came back with issues. Ended up finding out fast that they were junk.
I've heard of Hewitt but have no experience with them. Isspro & Autometer are ok but all mechanical pressure gauges either need a high quality fuel snubber or a needle valve, specially with any piston pump to absorb the pulsations or almost any gauge will live a shortened life. I would stay away from any electrical fuel pressure gauge. Prone to early life.
I personally don't bother running a fuel pressure gauge full time, just check fuel pressure once a year or longer, as you can't really hurt a p7100 pump if fuel pressure falls below needed pressure, you will feel the lose of power. Can't beat the reliability of a piston pump. I do carry a spare under my back seat but you know the drill. If you carry a spare, you will never need it. lol

A VE Inj pump is different, you drop to 0psi & it is hard to tell the difference as it pulls a slight vacuum, runs a much lower case pressure & runs ok with low psi, while you are slowly damaging the Inj pump because it is only cooled & lubed by fuel flow.
 

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Mr Hewitt of that company actually invented the pyrometer for diesels 60+ years ago. They also make aircraft grade instruments which we know those have to be top quality. Many of their gauges show up in semi trucks. Some of their interesting ones are dual reading gauges. For example, you can have a fuel pressure gauge that reads before and after the filter or a boost gauge with dual reading which would be idea on twin turbos. They even have dual pyros but those are mostly for multi engine aircraft. Not sure who are the primary makers of marine quality gauges. Those have to be water tight and non corrosive and take the beating and pounding a boat might give.
 

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Discussion Starter #16
Found another gauge new in the box same make size etc, it reads 5 lbs less than the first one. I'm inclined to believe this one. The first one had been mounted directly to the engine. A vibration test.
It still does the climb after shutdown but only up to 12 psi.
Video with gauge No 2:
[video]https://www.flickr.com/photos/[email protected]/47138471272/in/dateposted-public/[/video]

The Scout had set for 3 days had to prime it to start. This is getting old real quick.
The fuel filter was changed in 2012 after the IP rebuild, a new one won't hurt and I don't expect that to be a fix.
 

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Slight sidetrack.
The VDO company are OEM fit for a lot of vehicles and have a Marine line, as I found out even they can gave issues.
CAT also has the dual pyro's, had them on 3412's. Cannot remember ever having issues with CAT gauges and we ran a lot of units.
I did a water test on the 2 gauges and figured my compound was the closest to accurate and the VDO was off. Took both to the shop I purchased from and they tested both, compound accurate and the VDO was off. Out of stock so waiting for a new shipment

Cheers Steve
 

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Discussion Starter #18 (Edited)
The spiking lift pump pressure isn't.
The previous test was done on a cold engine, did the test with a hot engine, NO spike. False alarm.
Why the difference, no idea.
 

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I tend to use Isspro EGT, boost/drive pressure & trans temp gauges.

As far as fuel pressure goes - the cheap $19 Summit mechanical gauge seems to last 2-3 years, no different than the $75 Isspro gauge; even with my Autometer snubber + a 12" section of grease gun hose in series.

I do hear the older Hewitt fuel pressure gauges are excellent.
 

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The spiking lift pump pressure isn't.
The previous test was done on a cold engine, did the test with a hot engine, NO spike. False alarm.
Why the difference, no idea.
Glad you got it figured out.
 
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