jonathan
Full Access Member
i have a problem lol. at my fuel pump i have 6psi at the sharder valve i have 17 pounds of vac. i know you guys are going to say change the filter but the filter is brand new. so what can cause my issue?
fuel pressure
- Thread starter jonathan
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jonathan
Full Access Member
anyone?
Vfelix702
Registered User
wow any signs of leaking diesel any where?
redneckaggie
rebel w/o a cause
did you confuse the supply/return lines that is the absolute only thing I could think of and even then I dont think that could happen because this is an open system so how could it be sucking that much volume
The line from the lift pump to filter has to be plugged, the IP is pulling the 17 inches of vacuum. Are you getting the vacuum while cranking? No fuel to the IP will destroy it in short order. Check the fuel pressure from lift pump to filter at the filter connection.
It would be more clear stated like this. "At my fuel pump I have 6psi, at the schrader valve I have 17 inches of vacuum. Is that correct?
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jonathan
Full Access Member
yes that is correct. Check the fuel pressure from lift pump to filter at the filter connection. are talking about the line that goes from the filter to the ip? if so am geting 5 psi while cranking it over
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jonathan
Full Access Member
also i am geting that vac at a idle
jonathan
Full Access Member
no signs of leaking
DeepRoots
Tug Engineer
Obviously check for a blockage at the line from the fuel pump to the filter head. You *can* replace that with fuel hose if needed.
Not the problem?
Disconnect Fuel shutoff valve. Take the line from the fuel pump to the filter off (at the filter) crank over the engine and see how much fuel is delivered in a set time of cranking (lets say 15seconds).
Reconnect lines. Take line after filter off and route to a container, crank again for 15seconds and see how much fuel is delivered.
If it is different, either the filter is indeed clogged or something in the filter head is clogged (not so likely).
I also notice that you are running Waste Motor Oil. You *can* clog a filter in 5 minutes of running if the temperature is not right, or you did a really bad job of filtering. Most filters can plug up easily if there is an excess of water in the fuel. Running WMO when the engine (and filter) is hot works just fine, but when the engine is cold, the fuel gets very very thick and may not be able to easily pass the filter.
good luck
Drew
Not the problem?
Disconnect Fuel shutoff valve. Take the line from the fuel pump to the filter off (at the filter) crank over the engine and see how much fuel is delivered in a set time of cranking (lets say 15seconds).
Reconnect lines. Take line after filter off and route to a container, crank again for 15seconds and see how much fuel is delivered.
If it is different, either the filter is indeed clogged or something in the filter head is clogged (not so likely).
I also notice that you are running Waste Motor Oil. You *can* clog a filter in 5 minutes of running if the temperature is not right, or you did a really bad job of filtering. Most filters can plug up easily if there is an excess of water in the fuel. Running WMO when the engine (and filter) is hot works just fine, but when the engine is cold, the fuel gets very very thick and may not be able to easily pass the filter.
good luck
Drew
jonathan
Full Access Member
i ran all of the wmo out of the tank. then i changed the filter and put 20 dollars of diesel fuel in the the tank and about a half gallon of new atf and a whole thing of the white power service. also i am get 5 psi from the line that goes from the filter to the ip. and the line going from the pump to the filter is geting 6 psi . is normal for a little pressure loss? i am talking about before the filter and after the filter
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If your getting that kind of pressure in both places, then saying you get 17 inches of vacuum at the schrader valve, that would seem to be impossible to have a vacuum between two pressure points. Six psi into the filter five psi out of the filter, one psi drop across the filter element, 17 inches of vacuum, impossible. Your getting a false vacuum reading.
Why did you measure for pressure and vacuum that way?
DeepRoots
Tug Engineer
Agreed the vac reading is bs.... if you ever pull those three fittings out of the filter head, they don't really go anywhere special, just straight into the filter (some before, some after).
For future reference, a clogged filter, the engine can run fine it just looses power with acceleration. I've driven when a lift pump died as well. I *could* still drive (matter of fact I did) but it was at a top speed of 25mph
I wouldn't advise that, except I was about to rebuild the IP anyhow.On a slightly different note, don't get too crazy on the additives (atf/a whole bottle of power service). These engines are designed to run on diesel fuel.
so now the real question. What is wrong with your truck that you decided to test for fuel pressure?
Drew
TestDriver
Registered User
I think so as well. Your measuring method or tools or both are flawed. There is less than 15psi atmospheric air pressure where ever you are on this earth. If you're measuring for vacuum with a vacuum gauge that is absolute, I can see where you could see 17psi. At sea level, that would mean slightly more than 2psi positive gauge pressure. Or, in other words, it's the probable/calibration difference between the other two ports.
You cannot have more than absolute zero pressure for vacuum so you can't have more than about 14.7psi vacuum readings unless you are not starting from atmospheric. Based on your first post, you should probably try a different gauge. But, based on your last post, things seem to be fine.
Re: DeepRoots,
I can think of one scenario where driving with a clogged fuel filter could be bad. If you have an electric lift pump by itself on in conjunction with the mechanic lift pump, you could tear the fuel filter. It is not supported in the center and the pleats can just fold in and tear letting a bunch of crap go right into your IP. Don't ask me how I know, just look at some my past postings. I don't know what the limit is of the pressure the pleats will hold but I was running about 10psi to the factory filter.
jonathan
Full Access Member
i measured for pressure at the schrader valve and got vacuum. so then i decided to test the pressure from were the line goes from the filter to the ip and got pressure and it didnt make sense to me. i have one of those fuel pressure/ vac tester things
jonathan
Full Access Member
the reason i decided to test my fuel pressure because the "fuel filter" light came on. and i thought that that when that light comes on it reading vacuum so thats when i tested the fuel pressureAgreed the vac reading is bs.... if you ever pull those three fittings out of the filter head, they don't really go anywhere special, just straight into the filter (some before, some after).
For future reference, a clogged filter, the engine can run fine it just looses power with acceleration. I've driven when a lift pump died as well. I *could* still drive (matter of fact I did) but it was at a top speed of 25mph
On a slightly different note, don't get too crazy on the additives (atf/a whole bottle of power service). These engines are designed to run on diesel fuel.
so now the real question. What is wrong with your truck that you decided to test for fuel pressure?
Drew
