I have a two tank plant drive system in my 92 f 250. Recently due to a yet to be determined electrical problem my Vegtherm Mega that came with the kit stopped working. You would think that with a 26 plate FPHE I would still get OK temps before the IP but I don't. Here is the route the fuel takes.

Tank(hotfox) > vormax(filter) > HOH > 26FPHE > 3 port valve > lift pump> vegtherm > IP.

It is a looped system with a second 3 port valve controlling the loop. I usually warm the IP before switchover by looping my fuel before I switch to Veg. I recently replaced the thermostat with the hottest one I could get a 190. I know people say that a FPHE is the only way to go but without my vegtherm there is no way my temps will get above 140 at best on a warm day. I am currently within the next few days going to add a 16 FPHE pre vormax filter to aid with PHO oil in the wintertime.

Is there anything I can do to get my temps up without the vegtherm?

I would not mind doing away with it, but at this point I do not see how I could have acceptable temps without it. I should have it fixed in a few days.

This message has been edited. Last edited by: wydra,

Tell us about your plumbing of the coolant system. Where did you tap the coolant for the FPHE?

The coolant line coming off the engine near the front next to the alternator. It goes to the fphe under the hood then back through HOH to the bed of the truck and then back to the engine where I tapped into a coolant line off the manifold on the passengers side.

quote:

Originally posted by wydra:
The coolant line coming off the engine near the front next to the alternator. It goes to the fphe under the hood then back through HOH to the bed of the truck and then back to the engine where I tapped into a coolant line off the manifold on the passengers side.

That's the problem... the HOH is restricting the flow through the FPHE. The FPHE should have it's own coolant loop.
coolant supply->FPHE->coolant return

Something is wrong the FPHE has to have air in it. Or it could be mounted wrong. The coolant could not be flowing. You have an air leak somewhere that is cooling the fuel.
The 26 plate on my truck runs 180 under all conditions. Usually 190 around town.

I have just upgraded my fuel lines and insulated them really well going from the FPHE to the lift pump. The only time I was not getting really hot temp was traveling on the highway in cold weather.

You need to make separate taps of the coolant for each line that you are using (Ts). That way, each device (HOH, FPHE, fuel pick-up, etc) is getting its coolant heat without restriction and without previous heat loss. The FPHE is the most effective and most important. It is getting starved with your set-up, and it is not getting hot enough coolant.

I will try and post pics. in the next few days.

I am pretty sure though my coolant has its own loop. Here is how it goes.

Coolant line coming off top of engine T'd into > fphe > HOH > Filter > hotfox(tank) > HOH > T into seperate coolant line(this one goes into manifold on passenger side.

quote:

Something is wrong the FPHE has to have air in it. Or it could be mounted wrong. The coolant could not be flowing. You have an air leak somewhere that is cooling the fuel.

I do not believe I have an air leak but I am not sure. How would I find an air leak with my coolant system?

I think the fphe is mounted correct. It sits upright above the fender well inside the engine bay mounted on a firm piece of metal.

...that's repeating the same description...and the components are still connected incorrectly for best performance.

Both 240V and I have explained the problem. If you can't understand the problem, you're pretty well hooped.

The engine has a coolant pump with a pressure output side and a suction inlet side. Hot coolant must flow from the pressure side, to the FPHE and DIRECTLY back to the suction side, and not to anything else.

╔>=P==>╗ P=pump
╠<=H==<╣ H=heater
╠<=F==<╣ F=FPHE
╚<=T==<╝ T= HOH + filter+pick-up

Find someone near you with the same vehicle and see how it's is connected. Good luck!!

I should add that in summer on a 90 deg F. ambient temp. day if I am driving up a steep grade in 4th gear with WOT 3000 rpms +/- I do notice my fphe working I will get temps of 180 deg. F. I know its the fphe giving me that temp and not my vegtherm because going up hills with WOT(wide open throttle) the vegtherm does not put that much heat because I am drawing a lot more amps when I am flooring it thus taking available amps away from the Vegtherm.

I'll try one more time. Your current plumbing restricts the flow of coolant through the FPHE. That restriction makes it impossible for it to efficiently heat your fuel. The solution is simple: make a separate loop for the FPHE ONLY and you will achieve much higher temperatures. You will need to make an additional -T- in the coolant pump (feeding the coolant to the FPHE) and the coolant suction (returning coolant line) to accomplish this. The current -T- will need to be re-plumbed to connect to the HOH, etc.

You will get MUCH more heat to both systems. If you do not make this change, you will continue to experience what you have. If you do make this change, you (and your engine) will be very happy with the results. Everything else you have done is great.

Also, you must read this.

You've probably already done most of this, but in addition to the replumbing (which I also have done with good results on my 87 f250),make the sure fphe comes off the first "T" and the hoses are not kinked in any way.
Also try to increase insulation of the fphe and hoses. I would put a layer of foam between the fphe and the metal its bolted to. There is also a correct orientation for vertical mounting to prevent air accumulation. Mine's mounted flat just to the rear of the battery.
As for the vegtherm, I would expect it to have more current available to it with higher rpms going uphill.
One other thing is to have a way of blocking off the air flow in front of the radiator as the ambient temps drop. I just use cardboard, but will be upgrading to a zippered or snapped adjustable cover for this coming winter.
I'm also going to try to shield the vegtherm from the fan airflow.
Mike

This might sound like a dumb question, but are you sure you have plumbed your HE with a crossflow pattern instead of running both fluids the same direction?

My coolant loop goes through my hot fox, vormax, FPHE then through a coolant coil around my vegoil filter then back. I have full flow and plenty of heat. Since my FPHE is after my 6 port valve my startup fuel is run warm. It gets to 160* without any 12v heat. With the vegtherm mega I see 180*.

Don't mean to argue but a single coolant loop has served me well for the past two and a half years and it's only a 3/8" ID hose with a 13 plate HE!!!

Yeah..but you are in California. Those who live in less temperate climates usually need to focus more on heating VO than you may have to. Systems that work "fine" year round in temeprate climates tend to work only seasonally in cooler ones. I usually get a large number of "help..my conversion stopped working well" emails as fall progresses. In most cases it is because the conversion simply was not designed with cold weather operation in mind.

FPHEs are so efficient at transferring heat from coolant to fuel that optimum coolant flow rate may not be an issue in warmer climates. Bu in cold climates it definately IS.

quote:

Originally posted by hheynow:
My coolant loop goes through my hot fox, vormax, FPHE then through a coolant coil around my vegoil filter then back. I have full flow and plenty of heat. Since my FPHE is after my 6 port valve my startup fuel is run warm. It gets to 160* without any 12v heat. With the vegtherm mega I see 180*.

Don't mean to argue but a single coolant loop has served me well for the past two and a half years and it's only a 3/8" ID hose with a 13 plate HE!!!

My system is currently the same as hheynow's. I am assuming is plantdrive also.

This weekend I am going to T into coolant pump and run a seperate coolant loop for the FPHE and see if that makes any difference. I will let you all know how it goes.

Thanks for all the tips.
Darwin

Dana, Yes I'm in California but my system works great down to 18*F (the lowest temps we normally see).

Thanks to everyone for your help. I replumbed my system so the fphe has it's own loop. It works a lot better. Again, thank you all.

your friend,
Darwin

Glad to hear it, good luck!

Thanks for the positive feedback on what worked to solve the problem. One thing you could do to make this discussion useful for people with the same problem, is to go back to the first message and change the subject to "FPHE and low temps". That will make it easier to find for others having the same problem in the future.