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Fuel rail pressure

Gene Trask

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I am having trouble starting my roxor.
With a small shot of starter it crank right up. But will not without it.
It began after I changed the fuel filter.
I have since put a whole new filter case and filter on.
Running at idle my pressure is 3 to 4000.
Trying to crank I am at 1100 to 1900.
At rest it is at 21.8
Is pressure my problem?
 

txroadkill

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What are you using to get those readings?


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txroadkill

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I’ll check my pressures tomorrow to compare. Did you replace the o ring? If you took off fuel lines and removed filter housing to turn it over to swap filters did those lines seat back in correctly?


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Gene Trask

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The lines are not leaking, so I am assuming the sealed up.
I think my pressure on that side was 40. I will have to look to confirm that.
 

txroadkill

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The lines are not leaking, so I am assuming the sealed up.
I think my pressure on that side was 40. I will have to look to confirm that.


I have an 8v92 Detroit that I bought and it wouldn’t hold a prime. I replaced every fuel line on it and now it holds the prime. Granted the lines were probably the originals from 1981 but it lost prime overnight and didn’t leak fuel. You might push them in and see if they click. Maybe one of them isn’t seated all the way. And likewise double check the fuel bowl that it’s tightened all the way.
 

Gene Trask

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I don't know what the pressure on the tank fuel pump side is.
I don't se a sensor for that.
Not running my frp is at 21.8
And the baro 14.6
Map 13.2
I'm not sure if that helps.
I checked the bowl and it is all the way tight. I greesed the oring so it would go on better.
The lines seem to be on good.
 

txroadkill

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You can see the rpms and fpr. All readings sitting still. I tried checking pressure with key on and engine off and the pressures were slowing dropping to 0. Hope this helps.
 

txroadkill

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Have you run it much since this started? Maybe it’s taking awhile to get a good prime.
 

Gene Trask

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I have run it several times going out 30 to 45 min at a time.
When it started doing this it took a week or more, progressively getting worse. I could try bleeding the fuel lines to be sure there is no airlock or something.
 

Gene Trask

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Yes we do get fuel in barrels.
I have dropped the tank and cleaned it since then.
How about if I drain it again, put new fuel with additive in it and see what happens?
 

1BB

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Somewhere, you have a leak that's allowing your fuel system to bleed back down and losing its prime and causing hard starting.

If I were you, I'd clean every location where you removed a hose, screw, fitting, housing, anything in the fuel system when you changed your filter, and clean those areas CLEAN and make sure they're DRY DRY DRY.

Then get your vehicle started and let it run a minute or so and running smooth and then shut it off.

Then go to the fuel tank and remove the cap, and stick and air nozzle into the filler neck, and shove some rags around it to try and seal it up to some degree so you're getting 5 to 7 psi of air pressure pushing into the fuel tank. I'd even regulate my air down to around 20 or 30 psi coming out of the air compressor, just to be sure you don't overdo it.

Then after a minute or two of pressurizing your fuel tank and fuel system, go back to every location you cleaned and see if you see any diesel leaking at those locations. I bet you'll find your leak location pretty quickly.

AZ is right, don't use starting fluid in your engine if at all possible. In your situation you need to, but don't keep doing it. What starting fluid does, is washes your cylinder walls clean of oil, and when your engine cranks and goes on the compression stroke, that pressure forces the piston rings against the cylinder wall and without oil it will gouge the living hell out of both rings and wall. VERY quickly, you won't be able to start your engine without the starting fluid. Diesels can get addict to SF very very quickly.

If you do need to use SF in cold weather starts, do it like this......

1. Remove your air filter and set it to the side
2. Spray SF into the air filter housing, a 2 or 3 second shot for starters and see how long it burns
3. Light it on fire, and keep your face away from it
4. Go crank your engine while you have a good fire going

That fire preheats the air going into your engine and makes for very easy starting without damaging your engine with SF. You may have to do it a couple times depending on how cold it is. Don't worry if it's plastic because that plastic can handle HIGH engine temps, and besides, that plastic is as cold as the temp outside, and you have cold air passing through that plastic when cranking and the engine when it's running, so it will never melt. I mean you can hold your hand on the plastic and see it's nowhere near hot, let alone melting. Just don't sit there soaking it with can after can of SF, use a little common sense here. Besides, by the time you ever get that plastic to its melting point, you'll have had your engine running already.

Also, NEVER spray SF into the housing while cranking the engine. You do not want to risk getting that in the combustion chamber as raw fluid as it will wash the cylinders clean of oil.

Also, you don't want to risk raw fluid hitting a glow plug, because that can destroy your engine. It can break connecting rods, knock a hole in a piston, and even stretch head bolts and lift the heads from the block.

Starting fluid is a great tool, when used properly.

This is basically how old diesels were started in cold weather. They had a steel pipe that was part of the air filter housing that was between the air filter and the engine head, and threaded into that steel housing, was a glow plug. Next to that glow plug was a nozzle and hooked to that nozzle was a tube coming from a small hand pump on the dashboard. You would push a button and get that glow plug red hot, and pump that small handle for the hand pump, and that would suck diesel from the fuel line and spray the fuel across that glow plug and it would start a fire in your air filter housing and preheated your air going into the engine for easier cold weather starts. Now they just moved the glow plugs inside the engine in each cylinder, but they did start using them in the air filter housing before redesigning the engines.

Using SF in this manner is just going back to old school ways of doing things.

It worked great, but you had to have a working knowledge of glow plugs and not overheat and pop them, but this was back when Men had a working knowledge of things they owned, and nothing was automated.
 

txroadkill

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He may not find the leak by seeing fuel. My 8v92 had no fuel leaks but lost prime. I can’t explain it but sometimes the lines can loose their seal just enough that the prime is lost but fuel doesn’t leak out. Granted my fuel lines are the braided covered lines and I believe the Roxor will be all plastic. I still think it’s going to be related to the filter change. A couple years ago I did the filter on my 350 with an aftermarket one and the o ring looked different. I had long crank times to start it. Went back with a motor craft and the issue stopped. If memory is right the aftermarket filter o ring was shaped slightly different and I want to say even had the molding tits on it. Fuel didn’t leak out but air got in and prime was lost.

My opinion go back to filter and check the o ring. Next check the lines if they were disconnected. Remove them and inspect the couplings. They have o rings inside them I believe.


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Gene Trask

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Thank you I will try tomorrow to check all the lines again, do a pressure test and change fuel just be be thorough.
 

Gene Trask

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Wow ok got it going.
I did the pressure test and checked my filter and lines again. Then I drained the tank, and went to put different fuel in. Normally I pump from the barrel. This time I had out it in a 5 gal bucket. When I looked at what is had drained out and what I was about to out in..... The difference was obvious.
What I had drained out you could only see about 3 inches down in the fuel. What I was about to put in was completely clear.
After letting it run for about 10 minutes it cranked up almost normal. Used to you turn the key it cranked. Now it takes 5 seconds or so.
So... Is there a way to clean dirty fuel?
I ran it through a chamois cloth and it is still dark....
Thank you all for you help and patients with me. This is our only land vehicle right now, everything else is by boat. So I needed it running. Putting boat in and out of the water.
Thank you. Any help on cleaning fuel would be great.
 

txroadkill

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Gene Trask

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OK!!! Finally after so long I think I have it fixed.
In the end I believe it was the injectors leaking pressure, not allowing the fuel rail pressure to build up enough. Maybe a first it was just a little bit so I could start it and get the rpms going with starter fluid, but in the end i replaced all four injectors. May not of had to do all four, but I did not have the caps to put ont he fuel rail to seal off the different lines to see which was bad.
that gasoline that I ran through it first, then the water , then junk fuel. I hope to learn the lesson one of you tried to teach me.. Filter, filter, filter, and then do it again.......
Anyway, I have some good contacts in India if you want to order from there.... Praise the Lord for letting us get it going.
Thank you all for your advise....
 
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