Community Forums

DAS1M · 02-19-2014, 07:42 AM

Hi

I have a 2004 W22 with 8.1 Vortec, running on gas and LPG conversion.
Just experienced for the first time poor starting, on gas, but when running all is 100% on the ball. Runs well, pulls well, and sweet to hear. No codes or engine check light.

Tested fuel pressure at the rail and has 55psi which seems good to me, but as soon as i turn off the ignition, the fuel pressure drops to zero almost instantly! So the slow starting is the time it takes for the pump to get pressure back in the rail, this I can see on the gauge.

I believe the pump is in the tank but is there also a pressure (one way valve) somewhere to keep the pressure in the rail when the key is off?

When first turning on the key the pump runs and pressure comes up well then after about 3 seconds the pump stops and only runs again when i go to the start position (cranking).

This is the 2004 engine with a single fuel feed and no return so the rail has only a damper fitted.

Any suggestions? New pump, one way (non return valve?)

If its the pump has anyone found a supplier that has these as a fair price? WH seem to want over $500 !

M&EM · 02-19-2014, 10:47 AM

Quote:

Originally Posted by DAS1M

Hi

I have a 2004 W22 with 8.1 Vortec, running on gas and LPG conversion.
Just experienced for the first time poor starting, on gas, but when running all is 100% on the ball. Runs well, pulls well, and sweet to hear. No codes or engine check light.----

When first turning on the key the pump runs and pressure comes up well then after about 3 seconds the pump stops and only runs again when i go to the start position (cranking).

I had these symptoms several years ago. It was caused by the failure of the internal fuel pump check valve . Instead of dropping the tank and replacing the pump, I found an external check valve that I installed on the fuel line between the tank and the fuel filter. This has proved to be a cost effective repair so far. The check valve cost about $15 back then.
SUR&R Auto Parts (SRRCKV5) Fuel Line Check Valve

mgscott4 · 02-19-2014, 02:55 PM

Before I would add a check valve, I would change the fuel filter. They no longer sell the 3 port filter, now you have to by the 2 port and adapter. Then, in the future, you only have to buy the cheaper 2 port filter and reuse the adapter.

Full-Timers · 02-19-2014, 08:17 PM

Mine did the same thing and it turned out to be the fuel filter.
Strange because I thought a plugged fuel filter would cause running problems also.

M&EM · 02-19-2014, 08:23 PM

Quote:

Originally Posted by Full-Timers

Mine did the same thing and it turned out to be the fuel filter.
Strange because I thought a plugged fuel filter would cause running problems also.

FT, OP states fuel line pressure drops off immediatly after shut down. I don't think that is a symptom of plugged fuel filter.

dieselclacker · 02-20-2014, 09:08 AM

I would install an in line check valve. The fact that the pressure drops to zero as soon as ignition is turned off is indicative of this.

Dmorgan6375 · 02-21-2014, 07:47 AM

And one last option would be as you're getting ready to start it, turn the key on for about 5 seconds before you start it. This will allow the pump to fill the line prior to starting it. Just a thought, this is what I use to tell people when they would have a hard time starting their cars/trucks in the winter. Just MOHO here!

DriVer · 02-21-2014, 09:39 AM

Delay start strategies and check valves are proactive measures not required or they would be included in the procedures or as OE equipment.

If the machine does not start after you turn the key on and crank the engine, there's a problem. Find and or resolve the problem.

At 99,9832.2 miles indicated, all I do is turn the key on, continue through the start position and let go of the key.

I'm on my 2nd fuel pump. When the 1st fuel pump failed, the engine either quit while running and then, in time, it subsequently refused to start. Since the new FP - no more problems.

M&EM · 02-21-2014, 10:44 AM

Quote:

Originally Posted by DriVer

Delay start strategies and check valves are proactive measures not required or they would be included in the procedures or as OE equipment.

If the machine does not start after you turn the key on and crank the engine, there's a problem. Find and or resolve the problem.

Yes quite true.

The problem being an inadequate check valve in OE pumps.

An external check valve resolves that problem as well as the cost of replacement pumps and labor. Not to mention the many steps involved for additional mistakes to be made!

dieselclacker · 02-21-2014, 05:28 PM

Quote:

Originally Posted by M&EM

Yes quite true.

The problem being an inadequate check valve in OE pumps.

An external check valve resolves that problem as well as the cost of replacement pumps and labor. Not to mention the many steps involved for additional mistakes to be made!

Right on Marty!!