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Author Topic: Uh oh....Fuel pressure issue  (Read 4383 times)
wayneswirld2
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« on: February 18, 2010, 11:05:30 AM »

Hey y'all....now I've got a fuel pressure issue.  Went to pick up the bus that I bought, can't get her started.  If I spray ether, a NO  NO I'm sure, the engine will start...briefly.  Runs for about 5 seconds and the fuel pressure goes to about 10psi.  If I continue to spray ether in the air cleaner I can get the fuel pressure to about 30 psi, but it still doesn't run on it's own. 

Found that the previous owner had been running veggie oil with no extra filters and no heater.  Replaced both fuel filters this morning...still won't stay running. 

Now, since I really know nothing about running this bus...1988 GIllig Phantom transit with a 6V92T engine....I'm not completely sure that I've got the switches in the proper position.

Any ideas?

Wayne
Austin, Tx
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DaveG
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« Reply #1 on: February 18, 2010, 11:13:57 AM »

I'd make sure you are getting fuel to the filters, use the 5 gal bucket trick.
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wayneswirld2
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« Reply #2 on: February 18, 2010, 11:15:03 AM »

Might be a dumb question, but what is the 5 gallon bucket trick?


Wayne
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IF it ain't broke, don't fix it.  But then again, if it's on your bus...do some damned maintenance to it.  It'll break eventually.
bigjohnkub
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« Reply #3 on: February 18, 2010, 11:38:57 AM »

Wayne, call or pm rdbishop . He will assit you all he can. He is near you. That is the greatest thing about this board. You will get help if you ask.
  If you don't know how to pm , go to your 1st post about buying bus, scroll
down to his reply and click on his name. Then click on his e-mail and go to town.
  Big John
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« Reply #4 on: February 18, 2010, 11:52:03 AM »

How I PRIME A DETROIT DIESEL

First - here's the usual flow of Fuel in our buses

A - From the Fuel tank pickup to the "check valve" - The check valve is there to prevent fuel from running back to the tank on shutdown
"check valves can be anywhere between the pickup and the first filter - the usually places are the bulkhead - or at the first filter

B - the first filter in called the "PRIMARY" filter - that will be the one closet "in line" with the fuel tank - now it may not be the one that is physically closest 
to the Fuel tank - just look at the lines coming from the fuel tank and follow it to the PRIMARY FILTER - now - there will also be a return fuel line going
back to the fuel tank - if you follow that path that will lead back to the engine and not a filter - so go follow the OTHER fuel line

C - now that you found the "PRIMARY Filter - most will have a THIRD PORT on the filter housing with a plug in it - the plugs are USUALLY 1/4" inch pipe
thread (commonly refered to as 1/4 NPT - national pipe tread) - don't be fooled the 1/4 refers to the APPROXIMATE inside diameter of that pipe - this
is where you would install a 1/4 " pipe thread to BARBED (Lowes / Home depot / Ace) fitting to attach the hose and of the garden sprayer full of fuel

D - from the primary filter - next is the FUEL pump - followed by the SECONDARY fuel filter - to the engine (sometimes left and right side split off
       
E - The overflow fuel (fuel not used by the injectors - about 90% is not used) will return back to the fuel tank thru a very important "RESTRICTOR VALVE"
The RESTRICTOR is there to help maintain fuel pressure  (which is about a low of 15 psi at idle to a regulated  (by the fuel pump pressure relief spring) to 50-60  psi  at 1200 rpms and above - note the fuel pressure at the input side of the fuel pump and primary filter is about 6" to 12" of vacuum - that is the sucking power of the fuel pump  - 6" indicates a clean filter - 12" could indicated a clogged filter.

Fill the filter (primary and secondary ) with fuel - fill the garden sprayer with fuel - remove the spray nozzle from the end of the sprayer hose -
attach the garden sprayer hose to the barbed fitting on the primary filter with a hose clamp and GENTLY pump at least of the garden sprayers fuel into the engine -

IF a DETROIT DIESEL FUEL PUMP BECOMES AIR BOUND (no FUEL IN THE PUMP) THEY WILL NOT SUCK FUEL - this is why you need to push fuel into the primary - thru the pump and into the secondary and up to the engine to do a PROPER job of PRIMING YOUR DETROIT ENGINE


Pete RTS/Daytona
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« Reply #5 on: February 18, 2010, 11:58:11 AM »

I'm not completely sure that I've got the switches in the proper position.


That would be the first thing you need to do. Get your switches in the right position. Don't know anything about your bus, but if it has a rear run/stop switch that's in the stop position, it will probably act exactly as you describe. I would suggest you start it from the rear if possible, or have someone start it from the front, and watch the engine stop cylinder on the fuel cutoff. If it doesn't release, you'll never get fuel into the injectors.

This is not an uncommon problem for new bus owners. Not sure how long you've had it or what your experience level is here but most of us with a rear stop switch have done this at one time
or another.

craig


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Craig Shepard
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wayneswirld2
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« Reply #6 on: February 18, 2010, 01:52:35 PM »

Talk about a very helpfull bunch of people!  Thanks so much for your input, especially that from RTS/Daytona.  Man, what a detailed description of how to properly do this.  I was over at the bus earlier this afternoon and was trying to bleed the system completely incorrectly.  I was pushing fuel from the line that goes from the secondary fuel filter to the injector rail/head.  No wonder I got nowhere.  I'm guessing, from RTS's reply, that the fuel pump is air locked at this point.

This thing is being a beast to prime.

Wayne
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DaveG
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« Reply #7 on: February 18, 2010, 03:07:32 PM »

Usually if you can get fuel to the transfer pump, then it will go.
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Jerry32
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« Reply #8 on: February 18, 2010, 03:28:03 PM »

PO might have been using a fuel boost pump on veggie too
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« Reply #9 on: February 18, 2010, 03:58:04 PM »

Wayne

Actually I seen the RE-PRIME question soooo many times in my 8 years on the boards - I took the time to write and hopefully spell-check a good reply - I keep it in a file - and just cut and paste it into replies

no big thing -- been there / done that

didn't want anyone else to fall down the same hole that I fell down ;-)

Pete
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gus
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« Reply #10 on: February 18, 2010, 04:47:51 PM »

As a second to what Craig said, if you have a rear shutoff switch and it is off and you have air pressure, it won't start on fuel.

If you don't have air pressure it will start and run fine until the air builds up, then shut off. I found this out the hard way when I first got my bus!

Obviously you won't have fuel pressure if the engine isn't running.
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« Reply #11 on: February 18, 2010, 07:31:37 PM »

I'm guessing, from RTS's reply, that the fuel pump is air locked at this point.


It may be now that you've messed with it, but it wasn't when you wrote the original post. You said you had fuel pressure to 30 psi. You won't have pressure if you have an air locked pump.

Check your switches....
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Craig Shepard
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« Reply #12 on: February 18, 2010, 07:37:33 PM »

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Chopper Scott
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« Reply #13 on: February 18, 2010, 07:57:39 PM »

Beings Clifford is on the road I'll fill in for him. Pump the pedal 3 times and hold it to the floor.  Wink
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« Reply #14 on: February 18, 2010, 09:16:32 PM »

If I may share a bad idea - when my 8V92 did the same thing (started on ether, but would not run), it was the ECM. I do not recall if you mentioned if the engine had a module?

I hope you are not experiencing what I have just been through.

If you open the fuel return line, and make sure you have fuel flow there, then you will know whether or not the problem is a fuel problem or something else.

Hoping for the best
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