Anyone converted an OM647 to external lift pump?

[haasenpfeffer_93]

Planning ahead to a cross country road trip next summer and wanting to eliminate as many things as possible that could fail and be a pain to replace on the road. Wanting to do a preventative replacement of my stock in tank lift pump and would love to convert to a an external motorsports style Bosch pump while keeping the factory pickup and sump system.
Looking at the ubiquitous and proven Bosch 200 series but it's a good bit higher pressure than needed at around 80psi. My question is how picky would the factory low pressure system be on the om647 - ie does it have to be exactly in that 60psi range or would higher pressure maybe be ok? Or would i need to do Bosch 200 then an external regulator set to 60 psi? That would of course put the bosch running at its max pressure or using its internal relief valve all the time which wouldn't be ideal

 

[Midwestdrifter]

The regulator on the low side is a spring valve integral to the HPFP. That sets the pressure around 55-65psi. The system doesn't really care as long as their is sufficient flow/pressure to maintain that. An 80psi pump just means its rated for that, and probably has an internal relief around 85psi (the factory pump is similar).

Any external pump you install will struggle to pull through the factory lift pump. So it would need to be removed. You can probably replace it with a section of aluminum tubing or similar, but It will be a bit fiddly to match the diameters I suspect.

The factory lift pump is probably pretty similar to a bunch of factory pumps, but the mounting frame/sender assy is specific to the sprinter. So if you matched the pump itself you could carry a spare without taking up much space.

 

[marklg]

In my case, there was a leak at the top and when tightened the sender failed and the pump still worked, at about 150k. Just touching it may cause the sender to fail, and it only comes with a complete new pump. I would leave it alone and worry about other things such as these that have already gone or had issues on mine at 180k:

Transmission
Injectors
Harmonic Balencer
Struts and Shocks
Rear Diff Bearings
EGR
Charge pressure hoses and resonator
Viscous Fan Clutches

I would not consider a one off pump that may interact with the design better than the original, which does not seem to be reported to fail.

I would definitely do things like brakes, hoses and sensors that are known to fail, replacing with OEM or other known good parts.

Regards,

Mark

 

[haasenpfeffer_93]

The regulator on the low side is a spring valve integral to the HPFP. That sets the pressure around 55-65psi. The system doesn't really care as long as their is sufficient flow/pressure to maintain that. An 80psi pump just means its rated for that, and probably has an internal relief around 85psi (the factory pump is similar).

Any external pump you install will struggle to pull through the factory lift pump. So it would need to be removed. You can probably replace it with a section of aluminum tubing or similar, but It will be a bit fiddly to match the diameters I suspect.

The factory lift pump is probably pretty similar to a bunch of factory pumps, but the mounting frame/sender assy is specific to the sprinter. So if you matched the pump itself you could carry a spare without taking up much space.

Good to know, thanks. I was planning to remove the factory pump and install in its place a hose or pipe stub to act as a pickup. And yes totally get the not fixing something that isn't broken. with 405k on the clock trying to address things that would be a sudden breakdown and more than an hour or so labor to fix. the in-take pump / sender assembly would take a lot of space as a spare and my over-active imagination puts it as failing about 2000 miles from home with 24.5 gallons of diesel in the tank haha

 

[Midwestdrifter]

The factory pickup tube has a kinda fancy anti-cavitation setup, so just retain the factory pickup in the tank (same height etc). Otherwise I don't really see any technical issues with retrofitting an external pump. Do make sure its not excessively large or high flow, as you don't want to overload the factory fuel pump relay.

 

[LowBudgetT1N]

Man, this certainly seems like a bad idea to me. One of the best improvements to the T1N was the installation of the in tank fuel pump for the OM647. Easy fuel filter replacement, key on fuel priming, no fuel hose on the suction side, no entrained air bubble no starts. Ask the early years crowd how much they love their external lift pump setup. If you want to do a preemptive replacement, go for it, drop the tank and replace the pump with oem.

 

[Midwestdrifter]

Man, this certainly seems like a bad idea to me. One of the best improvements to the T1N was the installation of the in tank fuel pump for the OM647. Easy fuel filter replacement, key on fuel priming, no fuel hose on the suction side, no entrained air bubble no starts. Ask the early years crowd how much they love their external lift pump setup. If you want to do a preemptive replacement, go for it, drop the tank and replace the pump with oem.

Adding an electric external lift pump does not negate the advantages of the 647 system. The system will still prime with the key on etc.

 

[jrod5150]

647 fuel pump failure is pretty rare

 

[marklg]

647 fuel pump failure is pretty rare

What about the sender? That broke on mine and I recall one other forum member with sender issues. It's electronics are specially confirmally coated in the tank, not something you are likely to be able to fix.

Regards,

Mark

 

[jrod5150]

What about the sender? That broke on mine and I recall one other forum member with sender issues. It's electronics are specially confirmally coated in the tank, not something you are likely to be able to fix.

Regards,

Mark

Never had one fail. Id think human error of replacing the pump or tank seal (tank seal a common issue) and damaging the sender on reinstall is more likely. Probably just jinxed myself. Fuel pump sender failure incoming

 

[Bill B.]

Has anyone tried to retrofit the tank with an aftermarket sender and gauge. It wouldn’t provide any data of course but I’d love a back up to the odometer.

also… can I put a resistor in the sender circuit to keep the dash gauge from waving at me all the time?

 

[NomadEnergyClub]

If the factory gauge is waving, I would first check the sender connector and tank ground, then measure sender resistance while moving the float slowly. A fixed resistor will only fool the cluster into one fuel level and will not make a useful backup gauge. An aftermarket sender can work, but it needs to match the tank depth and resistance range, and I would avoid changing the pickup or sealing flange.

 

[Bill B.]

If the factory gauge is waving, I would first check the sender connector and tank ground, then measure sender resistance while moving the float slowly. A fixed resistor will only fool the cluster into one fuel level and will not make a useful backup gauge. An aftermarket sender can work, but it needs to match the tank depth and resistance range, and I would avoid changing the pickup or sealing flange.

I should have mentioned that. Sorry. I’ve already confirmed that my sender has failed. I’m just not about to drop $450 into a new pump just because the needle and idot light are always trying to get my attention.

If it’s a typical analog meter shouldn’t I be able to peg the needle “F” if I shunt the sender to ground?

 

[marklg]

I should have mentioned that. Sorry. I’ve already confirmed that my sender has failed. I’m just not about to drop $450 into a new pump just because the needle and idot light are always trying to get my attention.

If it’s a typical analog meter shouldn’t I be able to peg the needle “F” if I shunt the sender to ground?

It's not a pure analog gauge as it does the swinging thing. From this post:

Fuel gauge sender question - OM647

I’ve read up on the related posts and haven’t come across this particular issue i A experiencing similar conditions. 06 dodge sprinter back story: i dropped The tank to clean and replace some fuel line last year. After which the fuel warning light was on and after about 5-10 minutes the needle...

sprinter-source.com

50 ohms is considered full. I don't remember if it did any more complaining than the swinging needle and amber triangle when it was broke. The pump and sender had to come from Germany.

I get that you don't want to spend $450. Maybe you can find a used one somewhere. Unfortunately, the parts for these are expensive and they are old and not that reliable.

A friend told me two decades ago, nothing is as expensive to maintain as an old Mercedes. I got one anyway and he was right. We have spent $28k in maintenance and repairs over the last 9 years.

Regards,

Mark

 

[Bill B.]

It's not a pure analog gauge as it does the swinging thing. From this post:

Fuel gauge sender question - OM647

I’ve read up on the related posts and haven’t come across this particular issue i A experiencing similar conditions. 06 dodge sprinter back story: i dropped The tank to clean and replace some fuel line last year. After which the fuel warning light was on and after about 5-10 minutes the needle...

sprinter-source.com

50 ohms is considered full. I don't remember if it did any more complaining than the swinging needle and amber triangle when it was broke. The pump and sender had to come from Germany.

Regards,

Mark

Germany? I thought I saw them at euroSD

 

[Bill B.]

It wouldn’t bother me so much if I wasn’t worried about wearing it out before I need a new pump. I should probably just invest in a new pump and then have a spare but there’s a lot higher priorities for a meager budget this year.

 

[marklg]

Germany? I thought I saw them at euroSD

I tried to order from them but they didn't actually have it.

Regards,

Mark

 

[jrod5150]

$75 plus shipping for a good used pump if you want to go that route.

 

[Bill B.]

$75 plus shipping for a good used pump if you want to go that route.

Thats a great deal and thanks for the offer of it was one but I’m pinching coins for more pressing part issues that need replacing.

 

[NomadEnergyClub]

On the T1N sender circuit, low resistance to ground is the full end of the gauge range, so grounding the signal wire should drive it toward full. I would use a known resistor instead of a dead short though, since zero ohms can be outside the cluster range and may set a fault. Do the test at the sender connector with the sender unplugged, and be sure you have the signal and sender ground wires, not the pump power wires.