Poor running & fuel pickup for aux heater

[Jocklandjohn]

Anyone offer a perspective on this please?

I've got both air heater and water heaters (Eberspacher) in my 110. The water heater has been in there 15 years and works fine, the air heater only installed last year (works fine too).

For both I tee'd into the fuel line at the lift pump before the fuel filter as has been commonly suggested.

However although both heaters work ok  I've had an ongoing problem with the vehicle's running - ok at low to moderate speeds but runs out of steam at higher speeds. Injectors are serviced, new lift pump & fuel filter and fully overhauled FIP a few weeks ago (for the second time!).  I know my FIP was knackered and it was fixed, and the lift pump was faulty too, but its all tip top and shiny new and I'm still experiencing poor full-load running (going up hills specifically).

I'm starting to suspect this  could *possibly* be a fuelling issue and might be related to the tee'd heater lines. I've got clear pipe on the water heater and when the lift pump is operating it causes the fuel in the heater line to visibly 'bounce' up and down.  I'm wondering if the addition of the two T's to the fuel line is having an effect on the lift pump efficiency when the engine is running. I've checked all the pipe connections to the heaters and they appear to be tight so my initial assumption that air might be getting in seems rather unlikely. The Eberspachers wont fire up with air in the system as the heater shuts down and flags up an error code, and thats not happening so I'm *guessing* it indicates all is ok.  However...is it possible that the lift pump pressure is enough to pull air in somewhere down the heater line without it being obvious to the heater sensors?

As the heaters run ok its only the vehicle running that concerns me. Would an electric lift pump (which might be a good thing anyway as I've used 5 lift pumps in the last three years) be a good move as it might more reliably lift the required volume of fuel despite the tee'd take offs?

Or tap into the fuel line at the tank exit (on the side 110HT 1989)  and run a dedicated fuel line to the heaters?

Or tap into the tank at top (I've cut the rear tub floor already and put a wee hatch in it so can get access easily to the top of the fuel tank) and insert a  dedicated into-tank line for the heaters?

So I guess the wider question is - is it conceivable that the additional fuel take-offs are affecting fuelling at high rpms? 

 

 

[supaimpy]

Very unlikely to be the t's , heaters generally don't loose their prime . If you had fuel issues  you'd be experiencing smokey startups on the heaters. Do the heaters fire up first time each time rather than going thru the 2nd attempt start ?

The pump is a solenoid pump so whilst it can be overcome if you tapped into a high pressure line for instance, ( first real sign is fuel dripping from exhaust on the heater) the only fuel issues for pumps are when they get run out of fuel, or the filter in the end fitting gets clogged.

[Jocklandjohn]

52 minutes ago, supaimpy said:

Very unlikely to be the t's , heaters generally don't loose their prime . If you had fuel issues  you'd be experiencing smokey startups on the heaters. Do the heaters fire up first time each time rather than going thru the 2nd attempt start ?

The pump is a solenoid pump so whilst it can be overcome if you tapped into a high pressure line for instance, ( first real sign is fuel dripping from exhaust on the heater) the only fuel issues for pumps are when they get run out of fuel, or the filter in the end fitting gets clogged.

No, no problems with heaters starting at all, other than a couple of internal faults I've diagnosed and repaired - glow plugs etc. They start first time and reliably so. 

The "poor running" I'm concerned about is the actual vehicle, and I'm just curious as to whether I've created some sucking void pressure thingy (!) with the two tee's thats causing a partial starvation of fuel to the FIP at high revs causing sluggish performance. It may of course be as simple as a slightly clogged fuel line so I'm aiming for a dismantle and blow through at some point, but just wondered if I was overlooking something obvious.

I'm going to remove the cheap bluebox britpart lift pump I fitted in an emergency two months ago and fit a Delphi. I've had 5 lift pumps on it in the last three years and the difference between some of them (before they prematurely fail) is noticeable, so it may be that a  better quality lift pump improves things.