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Old 24-07-2020, 17:34   #16
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Re: Quick Diesel engine question

I’ve not seen every pump for course, but I’ve not seen a pump that you can’t pump through. They have an intake and an exhaust valve of course and when you put a vacuum on the outlet, they both are sucked open and the fluid flow though.
I certified an airplane, an S2R-H80 that had two inline electric pumps, if the primary pump failed, the secondary was selected, but in all cases fuel flowed freely through a non operating electric pump, in one case it was pulled, the other pumped.
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Old 24-07-2020, 19:45   #17
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Re: Quick Diesel engine question

Gear type pumps have no check valves of any kind and are very common. Virtually every car with fuel injection uses one. Do you think you can draw oil through an engine oil pump that is not being rotated ?


Its made out that every type of fuel pump sold is a diaphragm style pump when thats obviously not the case at all. I can assure you that the piston type solenoid actuated fuel pump on my Kubota 1105 T engine will not let fuel be sucked through it either.



So what will happen in the OPs case is not clear since it seems that he has 2 dead pumps. If he is able to blow through the electric pump from inlet to outlet, then it must have the check valves that you claim and can safely be left in the off position when not needed. If however, one cannot blow through from inlet to outlet, then the way this style of pump should be integrated would be in parallel to the regular fuel pump and not in series. That way the regular fuel pump still has access to fuel when the electric pump is off.
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Old 25-07-2020, 14:48   #18
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Re: Quick Diesel engine question

I’m surprised no one even asked the OP what type of electric pump it is ....


I’ve used a posi flow fuel pump hooked between the tank and the primary filter. The mechanical lift pump was able to pull fuel through the pump without the pump running.

So moral of the story... identify the pump and I’m sure one can easily research this... or just blow through the inlet like above ^ you can try sucking too to see if these is indeed a check valve to prevent backflow
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Old 25-07-2020, 15:28   #19
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Re: Quick Diesel engine question

I can assure you that the piston type solenoid actuated pump will allow fuel to flow through it. Those are they ones that tick slowly when pressure exists and sort of rattle when it’s free flow.
While I’m sure gear pumps exist for fuel, they are quite rare, they are called gerotor pumps by the way Gerotor Pumps

I beleve there may have been a few used in gasoline fuel injection, but now it’s usually turbine and vane pumps.
But that has nothing to do with this, this is remote mounted low pressure diesel pumps, not cartridge high pressure gasoline pumps that operate at 35 PSI or higher.
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Old 25-07-2020, 15:40   #20
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Re: Quick Diesel engine question

Quote:
Originally Posted by Chayal View Post
Iím surprised no one even asked the OP what type of electric pump it is ....


Iíve used a posi flow fuel pump hooked between the tank and the primary filter. The mechanical lift pump was able to pull fuel through the pump without the pump running.

So moral of the story... identify the pump and Iím sure one can easily research this... or just blow through the inlet like above ^ you can try sucking too to see if these is indeed a check valve to prevent backflow
There are inlet and outlet valves, Both of these valves will prevent fuel from flowing back. The pump is itself a check valve.
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Old 25-07-2020, 15:45   #21
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Re: Quick Diesel engine question

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Originally Posted by mlydon View Post
the electric was most likely installed for bleeding. Some of them (like specific facet solid state pumps) are specified as 'pass-through'. they sit in-line just fine. Power them up, and you have Insta-Bleed.

Beats the hell out of flipping the little lever on the lift pump a million times.....

Matt

What he said
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Old 25-07-2020, 16:50   #22
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Re: Quick Diesel engine question

This is the style of pump I am referring to

External Gear Pumps

The clearances between the gears and housing are in tenths so very little leakage or else it couldn't work in the first place.




Quote:
Originally Posted by a64pilot View Post
I can assure you that the piston type solenoid actuated pump will allow fuel to flow through it. Those are they ones that tick slowly when pressure exists and sort of rattle when itís free flow.
While Iím sure gear pumps exist for fuel, they are quite rare, they are called gerotor pumps by the way Gerotor Pumps

I beleve there may have been a few used in gasoline fuel injection, but now itís usually turbine and vane pumps.
But that has nothing to do with this, this is remote mounted low pressure diesel pumps, not cartridge high pressure gasoline pumps that operate at 35 PSI or higher.
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Old 25-07-2020, 18:04   #23
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Re: Quick Diesel engine question

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Originally Posted by Westcliffe01 View Post
Gear type pumps have no check valves of any kind and are very common. Virtually every car with fuel injection uses one. Do you think you can draw oil through an engine oil pump that is not being rotated ?


Its made out that every type of fuel pump sold is a diaphragm style pump when thats obviously not the case at all. I can assure you that the piston type solenoid actuated fuel pump on my Kubota 1105 T engine will not let fuel be sucked through it either.



So what will happen in the OPs case is not clear since it seems that he has 2 dead pumps. If he is able to blow through the electric pump from inlet to outlet, then it must have the check valves that you claim and can safely be left in the off position when not needed. If however, one cannot blow through from inlet to outlet, then the way this style of pump should be integrated would be in parallel to the regular fuel pump and not in series. That way the regular fuel pump still has access to fuel when the electric pump is off.

You sir are mistaken.

Current fuel injection cars have a check valve contained in the fuel pump preventing backflow and keeping the line forward under pressure when the vehicle is turned off. If this check valve fails the vehicle will resist starting until the requisite pressure is built up by additional running of the pump. This would also indicate that the pump mechanism is not one way in its mechanics. These are high pressure fuel pumps.

The lift pump is a low pressure pump. If the pump is an electric model listed for diesel, listed as a "pass through pump" it may well have been installed as a convenience for bleeding. A smart alternative to operating the tiny inefficient levers that are usually included on the mechanical engine mounted pumps.

As I mentioned earlier we have one as well and it has been suggested as an upgrade for back up and assist with bleeding.

Best Regards
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Old 25-07-2020, 18:19   #24
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Re: Quick Diesel engine question

In addition to replacing filters, you should also check if you have a ball style check valve on the INLET of your filter housings. I just learned about this the other day, as a result of forensics on a fuel starvation issue I had. After 33 years (!!! - imagine that!!!) there was a buildup of sediment, thick black gunk, that prevented the ball from operating and stopped fuel flow. I learned about this by reading the filter housing manual - RTFM. [IMG]file:///C:/Users/Stu/AppData/Local/Temp/msoclip1/01/clip_image001.gif[/IMG]I removed the housing, opened the cap to the ball valve and cleaned it out.
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Old 25-07-2020, 19:21   #25
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Re: Quick Diesel engine question

As far as "any other reason... "

a search of your engine model popped up a tuber video of a fellow who had a clogged intake ball valve in his Racor housing.

..so yeah like several already said fuel supply circuit.

Your pump ,

, appears to be a cam lobe operated diaphragm and as such should allow forward flow from an electric pump.

It is highly likely that the electric was installed after the engine mounted one failed. The electric ones are about $20.00 USD and although there are some aftermarket versions available now the OEM Yanmar parts are sometimes kinda pricey.

Best Regards
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Old 25-07-2020, 19:46   #26
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Re: Quick Diesel engine question

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Originally Posted by Secondshift View Post
You sir are mistaken.

Current fuel injection cars have a check valve contained in the fuel pump preventing backflow and keeping the line forward under pressure when the vehicle is turned off. If this check valve fails the vehicle will resist starting until the requisite pressure is built up by additional running of the pump. This would also indicate that the pump mechanism is not one way in its mechanics. These are high pressure fuel pumps.

The lift pump is a low pressure pump. If the pump is an electric model listed for diesel, listed as a "pass through pump" it may well have been installed as a convenience for bleeding. A smart alternative to operating the tiny inefficient levers that are usually included on the mechanical engine mounted pumps.

As I mentioned earlier we have one as well and it has been suggested as an upgrade for back up and assist with bleeding.

Best Regards

First we aren’t talking about high pressure gasoline fuel injected cars here.
However the check valves you speak of only prevent REVERSE fuel flow, by pulling fuel through a pump, it’s not reverse flow so the valves will be sucked open. Even then it depends on which make of cars, if you notice when you turn the key on in a GM if you listen you will hear a buzz and a click, thats the fuel pump pressurizing the system for start. After start engine RPM is sensed to keep the pump running so that in the event of an accident the pump doesn’t continue or run, Mazda senses oil pressure.
But this is all irrelevant to this discussion, every low pressure electric fuel pump that I have any experience with will flow fuel through it when it’s off. There may be some that won’t, but I bet they aren’t common.
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Old 25-07-2020, 20:43   #27
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Re: Quick Diesel engine question

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Originally Posted by Secondshift View Post
As far as "any other reason... "

a search of your engine model popped up a tuber video of a fellow who had a clogged intake ball valve in his Racor housing.

..so yeah like several already said fuel supply circuit.

>>>>>>>>>>>>>>>>

Thanks, exactly what my issue was. Not my "engine" but the same filter housing. Should be standard on every fuel filter housing. Mine didn't have a buildup below, just in the ball valve chamber. Good videos, coulda been shorter, reason I don't "do" YT.


Thx again.
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Old 26-07-2020, 06:31   #28
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Re: Quick Diesel engine question

Shopped for electric backups, backups, backup bout a year and a half ago.

Some specifically stated "Pass through" and others did not. Unclear if the ones I have were listed that way. I could not find the same model by number.

I found it disconcerting at the time but I still have the $ 20 bucks and the backups backup has only been out to polish the fuel ... so far.

When polishing it continued to flow in a siphon scenario and drain through when the intake was brought to air. Can't be much pressure to open the valves.

Regards
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Old 26-07-2020, 06:42   #29
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Re: Quick Diesel engine question

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Originally Posted by svspirited View Post
What he said
Agreed, OP is in search of a problem that has very, very likelihood of existing. A64Pilot also gives several good responses. Of all the things to worry about, this is not one of them. If the OP has not already learned to bleed the engine, it's time - the second pump will make perfect sense then (r).

Peter
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Old 26-07-2020, 07:34   #30
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Re: Quick Diesel engine question

Most likely failure of a mechanical lift pump is the diaphragm fails, if it fails it’s very likely to dump fuel into the engine crankcase, enough fuel in there and the oil / fuel level rises enough so that the crankshaft beats it into a foam, the foam level rising so high that it goes out the crankcase vent and into the intake, fueling the engine in a runaway.
If the mechanical pump fails, it’s best to plumb around it, or to remove it an install a block off plate.

Most likely a two bolt plate will fit.
https://www.amazon.com/s?k=fuel+pump...b_sb_ss_i_1_15
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