How long to purge?

[PreservedSwine]

I've recently built my WVO system using different parts rom different kit's, but I'm not sure how long it takes the fuel rail to clear out and purge the WVO back to the WVO tank.

I've heard anywhere from 20 seconds to several minutes??
I'm still "dead-headed"

BTW- I'm using the greasecar controller and greasecar solenoid valves.

This is on my 2003 7.3

Thanks,

~Swine

[Halitosis]

Originally Posted by PreservedSwine

...fuel rail to clear out and purge the WVO back to the WVO tank.

I've heard anywhere from 20 seconds to several minutes??
I'm still "dead-headed"

BTW- I'm using the greasecar controller and greasecar solenoid valves.

I dunno much about your system... or whether or not you are using the stock fuel filter in the valley or not...

... but if we are JUST talking abou the fuel rails inside the heads, then I can tell you that I purge for 10 seconds, pushing diesel through the heads and back to my WVO purge tank (about 10 feet of fuel line)...

.... then I let my truck run an additional 45 seconds at idle to make sure diesel fuel makes its way into the injectors.

Stock fuel filter is not used in my WVO system. If it's used in YOURS, then I have heard of folks needing something like 20-30 minutes of "idle" time to ensure that all the grease makes it out of the system on the 7.3L.

Halitosis

[PreservedSwine]

Thanks. Yes, I'm just talking about the rails. I thought it may have been longer. My WVO tank incorporates a separate filter (300 watt heated Racor 900FH) for the WVO.

Everything is finished except the Fass fuel pump won't be here till Thursday. As long as Fed-Ex comes through, I'll have time to install Thursday night.

[ToddT]

Like you, I'm not using the stock filter and am purging only the fuel in the engine. At first I would wait about a minute to shut down the engine. The next morning it would have a minor case of the romps at startup. I chalked that up to using 60% biodiesel. But, lately I've been giving the truck more like two or three minutes to burn the WVO in the heads before shutting down. No more romps the next morning even when temps are well below freezing.

Bottom line: our trucks at idle are very conservative regarding fuel burn. We're talking just a few ounces per minute at idle. I'm now giving it a mile or two of driving or at least two minutes at idle. No more romps.

[ajohansson]

Todd,

Are you deadheaded? I cant remember. I guess with a deadheaded system 2-3 minutes sounds about right. I have heard with a regulated return like 20-30 seconds. Does that sound right to you?

[ToddT]

Yes, I'm currently deadheading.

A regulated return would surely get it down to seconds but even then, it depends on the flow rate through the return. You need enough restriction to maintain fuel pressure in WOT settings yet not so much as to make a long purge.

I'm thinking the best test there would be a fuel pressure gauge (inside, with snubber to prevent fuel in the cab) and watch the pressure under heavy loads.

[hheynow]

Originally Posted by ToddT

I'm thinking the best test there would be a fuel pressure gauge (inside, with snubber to prevent fuel in the cab) and watch the pressure under heavy loads.

Why hasn't someone made a fiberglass reverse facing hood scoop somewhere on the cowl for a fuel pressure gauge?

[PreservedSwine]

Originally Posted by ToddT

Yes, I'm currently deadheading.

A regulated return would surely get it down to seconds but even then, it depends on the flow rate through the return. You need enough restriction to maintain fuel pressure in WOT settings yet not so much as to make a long purge.

I'm thinking the best test there would be a fuel pressure gauge (inside, with snubber to prevent fuel in the cab) and watch the pressure under heavy loads.

My fuel pressure guage. Now, what would the "test" consist of?
I'm dead-headed as well.

According to Frybrid:

Since the fuel is dead-headed in the fuel rails, any fuel in the rails must be consumed in order to make room for the incomming fuel which displaces it. ie; If you are running on Diesel and wish to feed the engine VO you must run the engine long enough to consume the fuel in the rails before any VO can be burned. This is not a big issue when switching to VO, however, when switching from VO to Diesel the engine will have to be run for 15 minutes or more on Diesel before it can be shut down safely. To avoid such long switchover times and correct the fuel starvation issue inherant in this motor, we have designed a completely new fuel system. This system takes advantage of the fact that Ford wanted to use one head casting to manufacture the heads for both sides of the engine. As a result each head has a fuel port on each end, normally one is blocked. We open these ports and feed fuel into one end of the head and out the other, so both heads are fed fuel at a rate 20psi higher than stock through a fuel selector valve, the fuel flows out the opposite end of the heads and into an adjustable fuel pressure regulator (FPR), the return from this regulator in turn flows into a valve which determines which tank to send the returned fuel to (Diesel or VO).

15 minutes seems long quite a long time for the rails to clear, but these guys seem like they know what they're talking about.

[PreservedSwine]

Here's a flowchart-
My purge cycle is about 20 seconds, but how long to keep runnnig before I shut down?

[ajohansson]

your purge time will be longer than 20 seconds if you are sharing the stock fuel bowl/filter. Frybrid correct in their statement, it may take you 15 minutes to get relatively clean d2 to the heads and you will still have some vo in your diesel. My gfs system was plumbed like this and i tore out the fuel bowl and putin itp's regulated return with fuel bowl delete. my new system will be much like the frybrid with 3 valves. just about done with it. itp's products are top notch with the best customer service.

Also fwiw, dpp/fass recomends a no larger than 144 micron filter on the vacuum side of the pump. looks like you are running a racor. is

[PreservedSwine]

Thanks for the info- do you have a link with the vacuum info? I'm unable to find it

Also, I'll heed your advice on getting rid of the stock bowl (when the time comes)- never been a big fan of the stock set-up. Does ITP's fuel bowl delete withstand the high temps wvo temps wvo corrosion?

Thanks,

~Swine

[ajohansson]

ITP's kit is all alluminum and stainless steel. It should have no problem with SVO temps. The vacuum info came from Dan at DPP. If you go to the FASS site and look at the prepump water separator you will see it is 144 microns. Good luck.