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Topic: Fuel Problems? (Read 1126 times) previous topic - next topic

Fuel Problems?

Any ideals where to start?

I replaced my original fuel water separator with a Racor 790r with an electric primer built in about 5 months ago.  I have put about 1500 miles on coach since then.  I started coach up and let run for about 15 minutes last week of August with no problems.
 
When I start motor now I Put fuel petal to floor and it will barely start and run for about 5 to 7 seconds at a max of 1700 rpm and then die, not spit and sputter just die.  Reprime and same thing happens.  I tried holding electric prime button down while DW started coach with same results.

I have put a new fuel filter on it, check gaskets on fuel water separator, and made sure solenoid is opening.
 
I have about 1/3 tank of fuel.  I ran generator for about 15 minutes and there was no problem.
The last item I check was the Fuel water separator O rings, and it did not prime with electric pump when no fuel in it although it had prime 6 to seven times with no problems with fuel in it, can I hurt anything by trying to blow air from fuel water separator to tank to check for any restrictions?

Can the lift pump cause this problem?

Larry Bradley 
1998 U 270
Larry Bradley
SOB
former 1998 U270
Build 5251
Jeep Grand Cherokee

Re: Fuel Problems?

Reply #1 –
My guess would have me looking at the Racor filter/pump setup, mine has the clear plastic filter you can see fuel flowing into, the big issue with this is after many years, you need to replace it as the "O" Rings on the top get dried out and start leaking, producing what your talking about. Getting O Rings locally does not seem to be workable, I never tried, but have heard they are not available.
Other things would not let you prime it, so back to the plastic filter, Think the part number is Racor 200100 .
FWIW
Dave M

Re: Fuel Problems?

Reply #2 –
Does sound like a fuel supply problem.

Check the secondary filter for restriction. It could be plugged. It's the big metal filter. I rare cases, I have seen water collect in one of these and rust a hole in the bottom allowing diesel out and air in but most of the time, they are just clogged with sediment or algae (or both).

Try cracking a fuel line at the highest point at the main injector pump and then using the electric pump, evacuate any air in the system. Some engines are difficult to get all the air out of the fuel system. You could also leave the injector pump supply line off (into a container), run the electric pump and see how may liters/minute you get out the hose.

I had a electric supply pump develop an internal air leak. Check to see if you have any diesel on the outside of the electric pump. Plug one end and use a MittyVac to check for leaks in the pump.
 
You could isolate the Racor filter assemble and then using a MittyVac, pull a vacuum on the filter to see if there are any leaks.

If no leaks, plug Racor inlet and pull vacuum at the injector pump fuel supply inlet to check for leaks in the supply line, both pumps and secondary filter all the way to the Racor.

Check engine oil level and smell the dip stick for traces of diesel. Mechanical pump diaphragm could have a crack/hole letting air in the system, diesel into the crankcase. Oil level that gets higher is always a clue.

Examine the check valve that keeps fuel from flowing back to the tank. I had a crack in mine.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Fuel Problems?

Reply #3 –
Pierce,
I laugh when read about the MittyVac, I have one that does both the Vac or pressure, since I taught my employee about its nify capabilities, I can't find it, turns out he put on the van and he uses it alot, so thanks for the little chuckle  ;D
As you know, there are some tools that work great once you learn what all you can do with them.
Dave M

Re: Fuel Problems?

Reply #4 –
If the coach is an early 98 with a C8.3 Cummins, it could have a bad King Control.
The selected media item is not currently available.Bill&Doris 97 U270 36'
University of Parris Island Class of 66
Semper Fi  Build# 5174 MC#17094

Re: Fuel Problems?

Reply #5 –
Quote from: Bill Willett –
If the coach is an early 98 with a C8.3 Cummins, it could have a bad King Control.
Could be sucking air or a bad or dirty fuel  shut off solenoid.  Mine got to where it would not start at all and was the fuel shut off solenoid.  With the C8.3, clean the end of the shut off solenoid and it was fine.  Usually the solenoids them selves do not go bad.
1994 U225
build #4514

Re: Fuel Problems?

Reply #6 –
What about the lift pump. Is that leaking?
2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
Former Coaches  covering. 360,000 miles
1999 34 U270
2000 36 U320
2001 42' double slide U320
2018 Jeep Rubicon

Re: Fuel Problems?

Reply #7 –
I have a number of O-rings for the older model Racor fuel/water separator system, should anyone have a need. I replaced that system with the newer system some time ago.

Re: Fuel Problems?

Reply #8 –
Our faulty fuel shutoff allowed us to start fine, but because solenoid only opened a little, we could not get enough fuel flow to drive above 10 miles /hour.

We changed fuel filters, etc until we found our problem.

Cummins has a much improved fuel solenoid for our C8.3 that we installed ourselves. It comes with a new bracket and plugs into the same wiring harness.

Solenoid has two coils, one activated by starter-power to fully PULL up plunger, and one activated by ignition-power to KEEP plunger up.

These solenoids do go bad, and when it does, for a temporary repair, just tie it in fully open position to start and run and remove tie to turn engine off.

We did this for over a week until we could get parts.

Re: Fuel Problems?

Reply #9 –
There is a spring inside that solenoid that has a tendency to break. Two things can happen. It can shut down the fuel supply completely so the engine will not run. If the spring is hanging up, the engine will run at idle but not at throttle because the rack is not getting enough fuel to add torque. To troubleshoot the solenoid is a simple procedure. Take it off or separate it from the actuator arm and wire the rack fully open. This does not mean the engine will run at full throttle, just that it won't shut off until you release the arm. If this solves your problem, replace the solenoid. They are way cheaper on Ebay than a parts store.
1994 U280, Build 4490
Deming, NM.

Re: Fuel Problems?

Reply #10 –
Quote from: Twig –
They are way cheaper on Ebay than a parts store.
I picked up mine at the shop who does my service.  They had a bunch left over from when they use to service UPS trucks.  Got it for $35.  I had puchased a Fuel Shutoff relay thinking that was the problem but found out that those are not used on motorhome applications.  On mine it was the shaft of the actuator arm had gotten all gunky.  Just cleaned it up and everything was fine.  You might just need a new rubber boot.  The boot holds the solenoid together and keeps out debris that can keep your truck from continuing to run after startup. If your truck starts then dies when you let off the key, this could be your problem. If your boot is deteriorated this is the quick fix you need.  Here is a place that carries just the boot:  LarryBs.com.  But I can not find the boot on his site, but he has them at Dodge Diesel 5.9L Cummins Fuel Shut Off Solenoid Boot | eBay. 

But I think on mine the part on the pump that the square rod activatior attacted to was the problem.
1994 U225
build #4514

Re: Fuel Problems?

Reply #11 –
Update on fuel problems.
 
Thanks for all of the great ideals to locate my problem.
 
I took a 5 gallon bucket from home depot and by cutting hole in bottom and pushing fuel hose through it made a "portable fuel tank".  I plumbed the portable fuel tank in to the lift pump to eliminate any low pressure air leak problems.  My engine still would not run more than 10 seconds.

By opening valve on bosch injection pump and cranking on engine I verified I was getting fuel to the injection pump which meant Fuel Solenoid and lift pump were working.

My problem was solved when I replaced the 2 check valves in fuel system, I do not which one was bad as I replaced them both at the same time.
 
The fuel overflow valve is on the injector pump and has the hose for return fuel line on it. I had to move AC compressor out of the way to replace it.

There is a check valve on the secondary fuel filter head.  Both check valves have banjo fittings on them.
Larry Bradley
SOB
former 1998 U270
Build 5251
Jeep Grand Cherokee
 

Re: Fuel Problems?

Reply #12 –
Larry,

Well I guess the good thing about all this is that you now have a thorough understanding of the fuel system, something I'll probably pick up beside the road one of these days.   

Reading your post I'm thinking that the check valve on top of secondary filter on my coach is not working as fuel drains back and air goes in when filters are changed.  Seems to be impossible to purge it with the manual fuel pump.  Does this sound like a possibility to you?

Chuck
"Not so  long ago we were a nation of risk takers, riding five million pounds of  thrust straight into space."  Joe Gresh
Chuck Pearson
1996 U295
2018 Can Am X3 TurboRS