Teach me about pusher pumps

[Jan-78FJ40]

Hi Greg,
Did you wire yours over a relay or directly to a ignition-on power source? Did you put it close to the tank or close to the fuel filter? And finally, what did you mean by 'just keep it under the numbers discussed'?
Thanks,
jan

 

[crushers]

pusher pumps must be mounted as close to the tank as possible
hence the name "pusher" ...

 

[Jan-78FJ40]

pusher pumps must be mounted as close to the tank as possible
hence the name "pusher" ...

Thanks Wayne! It could be interpreted as 'anywhere before the injection pump in order to push fuel in there', hence my question.
cheers,
jan

 

[markthemenace]

sorry double-tap...

 

[markthemenace]

They reduce the wear/strain on the lift pump in your IP. If you install one, it is important to buy a pull-through designed pump which allows fuel to flow even if the electric pump is not working.

Summit racing sells the Airtex (USA made) pumps at a very good price. Both 24 volt http://www.summitracing.com/parts/ATX-E8131/ and 12 volt http://www.summitracing.com/parts/ATX-E8153/ applications. I know some 24V guys who have been running one for over a year with no issues. The advertised pressure is a bit high. However, manufacturers tend to exaggerate the PSI. When properly fitted close to the fuel tank, the PSI at your IP will be considerably lower as the resistance from the fuel pipe and filter will reduce the PSI. The main reason of concern with having a high PSI is that there have been reports of high PSI at the IP on a rotary pump advancing the pump timing.

Hmmm, interesting. That looks just like the one that goes for sale in PA for about $30 I think (or less). I know cos I bought one and used it in my VW bus...still running strong after 5 years with no issues.

How can one tell if its a "pull-through" design though? The other question is, how would one wire it...come on at glow, and keep running until engine is killed?

 

[crushers]

actually no, that is not the case.
in the instructions it states "as close to the tank as reasonably possible"

<grin>

 

[Tapage]

interesing I got mine pretty close to the pump ..

 

[finderscuba]

interesing I got mine pretty close to the pump ..

Mine is only about 5 inches before the filter. I installed it under the hood for simplicity and it's worked great at eliminating cold start fuel starvation problems.

 

[gerg]

As wayne said, put it as close to the tank as possible. The further you have it from the tank the greater chance you risk sucking small amounts of air into the line due to the negative pressure before the pump which will untimately translate into lower injection pressures at your injector.... leading to less than ideal spray ... higher egt... more smoke... less power...blaa blaa blaa.

The lift pumps on these injectors are quite adequate for the job. Installing the pusher pump, in my mind, is to avoid entraining air. Putting it far away from the tank defeats the purpose. All the extra power people feel might just be better injection pressure. Having a vacume in your tank, as some people have comented on in the last little while, will just exaggerate this process.

 

[roscoFJ73]

Installing the pusher pump, in my mind, is to avoid entraining air. Putting it far away from the tank defeats the purpose. All the extra power people feel might just be better injection pressure. Having a vacume in your tank, as some people have comented on in the last little while, will just exaggerate this process.

I dont understand how the stock system would "entrain" air?
The pickup is at the bottom of the tank.
Vacuums in tanks are a problem best solved at the source,usually by fitting a new/correct fuel cap or by clearing the blockage.

 

[roscoFJ73]

cold start fuel starvation problems.

Thats a new one.LOL
This is better known as an air leak that allows the fuel line from the pump to the filter to empty.
I had this until I replaced the fuel lines and clamps with new ones.

 

[roscoFJ73]

my theory and since i hate the word theory, take it for what it is worth, is that it allows the factory pump do what it is supposed to do, pump fuel to the injection pump.

<shrug>

So whats actually stopping the pump from doing just that?

The fuel pump is rigidly connected to the engine,nothing short of crunching metal is going to slow the pump down.
As I mentioned before ,the FSM says the feed pump can pump up to 54 litres an hour(it actually says 900mils a minute) ,its hard to see how the fuel pump would be starved of fuel with that much passing through it.

How much more fuel can you pump into a fuel pump that is already full???


Im still running the original fuel pump at 280000klms and it can still push the 75 to 130+ ,although I dont do this regularly.
No pusher pump and no fuel starvation here.

 

[roscoFJ73]

Kinda figured you would show up on this one roscofj73. lol.

Yup, there are thoughts in both directions for sure. Not being a tech, nor guru I cede to those I believe should know. And I've heard from two Bosch Rotary VE re-builders now that they bench test with PSI supplied to the back side of the pump (read to the inlet on the feed pump),

AFAIK,all test benches have that feature because not all injection pumps have their own feed pump.

and when asked about supplying fuel with a low PSI pusher pump responded it will not no harm and in fact is "probably the best thing you can do to keep the pump off my bench".

gb

Im still trying to fathom this one.The feed pump is on the main shaft,it has to spin around whether it has a pusher pump or not.

The injection specialists I asked both said the other components in the pump,the ones on the high pressure side,are the 1st to go.
Ive yet to see anyone on this forum or any other say" my feed pumps worn out but the rest of my fuel pump is good"
Its always the other way round.

The blades or vanes on the feed pump are spring loaded and about 12mm long,so they are not going to wear out overnight.

 

[crushers]

like i said, <shrug>, it just seems to help and i run them.

Rosco, i do things that seem to help. sadly, most of the time, i don't care what the reasoning is behind it.

 

[gerg]

My info on sucking air is just from a local old guy who rebuilds pumps and does injector work. He happens to love cruisers too. He totally recommended positive pressure on the feed line up to 5psi or so. He only testes pumps with positive pressure on the feed line to get the most accurate results. When he explained it to me it all just made way too much sense.

 

[roscoFJ73]

My info on sucking air is just from a local old guy who rebuilds pumps and does injector work. He happens to love cruisers too. He totally recommended positive pressure on the feed line up to 5psi or so. He only testes pumps with positive pressure on the feed line to get the most accurate results. When he explained it to me it all just made way too much sense.

If the DENSO rotary pump is making 5-7psi as it is supposed to ,why would you need any more pressure?
Any extra just sends it back to the tank.
If there was air in the system ,it could only come from leaking fuel lines.

I suspect this type of thinking is based around some of the older north american pickup trucks that had problems sucking enough fuel through to the pump.
But I am still trying to find a Landcruiser rotary fuel pump that suffers from fuel starvation.

 

[roscoFJ73]

like i said, <shrug>, it just seems to help and i run them.

Rosco, i do things that seem to help. sadly, most of the time, i don't care what the reasoning is behind it.

I care about the reasoning behind things ,and so far,I have not seen any .

 

[gerg]

If you care enough to add a pusher pump you might as well put it at the tank. Its not that much more work. Most of us have 20+ year old trucks, so I suspect there just might be a leak here or there. To me this is so straight forward its a no brainer.

 

[roscoFJ73]

My info on sucking air is just from a local old guy who rebuilds pumps and does injector work. He happens to love cruisers too. He totally recommended positive pressure on the feed line up to 5psi or so. He only testes pumps with positive pressure on the feed line to get the most accurate results. When he explained it to me it all just made way too much sense.

I read up on this and the reason diesel pump techs add a feed pump to the testing bench is that they have to have a constant pressure in the fuel lines to set the internal fuel pressure accurately,its 2.8psi on 1PZ 1HZ and 1HD T.
Nothing to do with air or any of the other reason put forward.

 

[roscoFJ73]

If you care enough to add a pusher pump you might as well put it at the tank. Its not that much more work. Most of us have 20+ year old trucks, so I suspect there just might be a leak here or there. To me this is so straight forward its a no brainer.

If you care enough about your 20 yo truck you would fix the leaks as a matter of priority ,rather than take the lazy way out and add a pump,to me thats a no brainer.
Leaks only get worse and pusher pumps only add more pressure to the fuel lines,so the leak will get worse even quicker.
And in the end you will still have to fix the leak