I am about to put a 30"HG vacuum gauge between the IP and the spin-on Fuel filter.

I have one worry, let me know if it's valid. Here it is:

I'm using a T fitting 1/2" NPT to 1/4" for the Gauge and 1/2" NPT. The fuel line from the Spin on is cut and the tee is going in between the two using fuel line and barbed fittings into the T.

My concern is that if parts of the gauge come out, it'd kill my IP. Is this likely? Should I do anything preventative? Maybe a screen filter of some sort before the IP?

Just wondering if this is undue worry?


Now why would I do this??? I just had my spin on completely clog to where the car would not run at all. I couldn't even blow through the filter (using a piece of tubing threaded into the hole in the center of the filter. The car stalled and of course with no fuel flow left me, my 3 kids, and wife stuck on a dirt road watching cows walk by. Since you can't see in the spin on, it'd be nice to know when it's ready for a change. I just changed the original about 1000 miles ago. There was LOTs of black looking crud in the pre-filter. I'm assuming it's Algae. I didn't see any in the tank strainer when I pulled that today.

__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

What you are interested in doing is to install a fuel pressure gauge between the secondary and the IP. A vacuum gauge will tell you nothing because there will never be any vacuum in that line.

With a pressure gauge installed, you can derive a baseline fuel pressure under normal operating conditions. When the pressure starts falling due to a partially obstructed filter, you'll see it on the gauge before the vehicle suffers a performance loss.

However, usually the vehicle will let you know that it's beginning to suffer from fuel starvation. Idle becomes "lumpy" or there is insufficient performance at maximum power levels. If you are attuned to the vehicle, you'll know that the filter is compromised prior to the point where it leaves you on the side of the road.

I've got an interesting story about the SD.........now that it has a brand new tank screen. It can go nearly 600 miles on 20 gallons. However, at about 530 miles I begin to get somewhat concerned. The vehicle will lose power after a hard right hand turn. So, I can continue onward and risk it.........or I can just visit my local ripoff NY station and put in three gallons until I get to CT.

The point of this story is that the vehicle will usually provide some notice to you.........if you're paying attention.

Or.......install a fuel pressure gauge........15 psi is more than sufficient.

Brian is correct, you need a pressure gauge. A vacuum gauge could only be used before the lift pump.

Filters are so cheap I usually change my pre-filter every oil change and my secondary spin-on filter every other oilchange, sometimes every three depending how dark my clear return lines look

__________________
RIP: 80 300SD
RIP: 79 450SEL
2002 E430 4matic (212,000km)
2002 ML500 'sport'

____________________________
FACEBOOK: PANZER450

So guys... let me get this straight... If the secondary fuel filter is completely clogged the IP is not working to draw fuel? In other words, the IP doesn't pull fuel at all? Will it hurt the IP to work when it is starved of fuel from the Secondary filter being plugged??


With a Pressure gauge, could I put it between the lift pump and the Secondary Fuel Filter? I'd assume if the filter is clean and new, I'd get a few PSI from the lift pump and when it's clogged I'd get a much higher pressure. Am I better off putting the pressure gauge between the spin-on and IP?


On warning signs... I really didn't notice anything weird. I had a smooth idle, I had very good performance on acceleration the day before. The stall came on very quickly. It was sputtery the morning I took it out, and that was it. I thought it was because it was cold outside. About 5 miles down the road the filter plugged and would not move an inch. I looked at the prefilter and saw some black specs that looked algea-ish and pulled the spin on and I couldn't even blow through it with the length of tube I had in the tapped part of the filter. Of course I had no spare with me (my mistake). I tried to blow out some of the clogging to no avail. But this is what made me consider the gauge. Probably not necessary but it'd be cool to have.

__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

As far as I am aware, the IP doesn't draw fuel. If you provide the IP with fuel, it will deliver the fuel to the injectors, but, it doesn't have the capability to draw fuel.

If the IP is starved of fuel, it cannot provide sufficient fuel to the injectors as requested by the driver.........so the vehicle won't accelerate.

If the IP is completely starved of fuel, the engine won't run. Apparently, you are a testament to that phenomenon.

Neither situation will hurt the IP in any manner.

You could put the pressure gauge between the fuel pump and the secondary filter.........however, I'm not convinced that you'll get a significant pressure rise if the secondary is blocked. If you put the gauge between the secondary and the IP, you'll definitely see a pressure drop if the secondary clogs.

Don't forget that the lift pump works in pulses. Whatever gauge you use after it will wear out faster than normal because of the pulses frequently working it back-n-forth.

The fuel pressure between the filter and the IP is over 15psi. Usually around 22psi. You may also need a gauge snubber to reduce needle bounce. Don't forget the risk of running fuel to the gauge if you use a mechanical gauge.

__________________
Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY

Ok... maybe I'll just forget about my handy gauge idea and just pay $7 for an extra wix filter for the trunk and tape a cheap 19mm wrench and pair of nitrile gloves to it

and... teach my wife the emergency routine should it ever happen again.

That sounds much easier and costs about the same or less!

__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

btw... thanks for the tips everyone. As always, I find people who know their stuff on this forum. It's always fun!

gotta love the smell and sound of a diesel! Wouldn't trade mine in for a gasser any day soon. And if it breaks, it's not terribly hard to figure out what went wrong: Fuel on time+ air+heat from compression=easy to fix (usually). That's why I drive these things! And MB made some of the greatest old diesels ever built! The more I work on mine, the more I appreciate the engineering!

__________________
-E300d '99 350k
-Suburban '93 220k
-TDI Jetta '03 350k
Sold
-F250 '96 7.3
-Dodge Ram 12V
-E320 '95 200k
-E320 Wagon 1994 155k
-300d Turbo '87 187k miles
-E320 1994 200k
-300d Turbo '84 245k (sold to Dan62)
-300d Turbo '84 180k
-300sd '80 300k
-7.3 Powerstroke Diesel 15P Van 500k+ miles
-190d '89 Non Turbo 2.5 5cyl 240k (my first MB)
Tom's Imports of Columbia MO Ruined the IP in changing leaky delivery valve O-Rings - Refused to stand behind his work. Mid-MO MB drivers-AVOID Tom's.

Thanks. I didn't realize it was that high. A drop in pressure due to the filter beginning to clog should be obvious at those levels.