Internal Pressure regulation in Bosch VE pump

[Johnnojack Senior Member Find all posts View Profile Close Johnnojack]

A thread commenced recently that asked for ideas on the best Walbro pump to supply low pressure to the inlet of injection pumps. This thread developed into a discussion on internal IP pressure regulation and how to address it.

I have pasted suitable posts from the other thread which can be read in it's entirety at http://www.biofuelsforum.com/svo_use...lbro_pump.html
To discuss Walbro and other pusher pumps, use the other thread.
To discuss the reason for needing a pusher pump with a Bosch VE pump, use this thread.

Tim - Moderator

I am a little intrigued by the eagerness of many here to install pusher pumps on engines which already have their own lift pumps. These lift pumps mostly vane pumps built in to Bosch VE pumps by the factory are more than capable of drawing the fuel from the tank. However many have reported increased performance from their engine by fitting a lift pump. Why? Well I will try to explain what is happening. The maximum output pressure of a pump is directly related to the input pressure which can be either positive or negative. The pump will have a multiplier effect. For instance if a Walbro pump is pushing fuel to a VE vane pump then the vane pump in the VE will have a positive intake pressure of say 4psi. Consequently the output pressure of the vane pump (the Injector Pump internal pressure) will be increased by using a pusher pump.
If there is no pusher pump then the VE will be working on a negative intake pressure i.e. a part vacuum and the resulting internal pressure of the pump will be lower.
This is only half of the story as there is the high pressure piston to come. This is another pump which when subjected to increased internal pump pressure will in turn produce higher pressure, in this case injection pressure. Result more fuel = more power.
Now the interesting bit which some seem unaware of and others have maybe forgotten, is all VE pumps are fitted with a regulating valve. Inline pumps have them too though some are part of a separate lift pump. If the regulating valve has a leaking O ring or is no longer set correctly then the internal pump pressure and subsequently injection pressure and engine performance will be down too. Fitting a pusher pump can fix the deficiencies of the regulating valve and restore performance of the engine. However simply replacing a faulty O ring or resetting the regulating valve can do the same thing without the expense and complexity of a pusher pump.
See link to photo of regulating valve and broken O ring, with new 90cent Viton ring. The removed hoses in the same pic had gone soft and leaked air from the effects of biofuels.

[Bueff Biofuel Enthusiast Find all posts View Profile Close Bueff]

Re: Any particular walbro pump?

Thanks for your help guys,

JJ I thanks for the photo, I have had a few hoses looking like that and have replaced them. I am rather hesitant regarding taking the IP apart just haven't had enough experience with these matters an I guess if I take it to a 'specialist" he is going to tell me that my pump is buggered due to the biofuels. Are there any manuals specifically for IP's? The 3L IP is rather common, so there should be something around?

Cade, that sounds like a good setup, I'll keep that in mind.

[cuppatea Senior Member Find all posts View Profile Close cuppatea]

Re: Any particular walbro pump?

Initially I followed the dual pump concept for a couple good reasons but after reading some comments (probably from JJ) about the VE lift pump I myself decided to simplify and let the VE lift do all the work. Using a looped return I figure the load from tank on the VE will be less than before (0.2L/min rather than ~5L/min). Apparently the VE pump has enough power to pull WVO all day. Only problem is chasing air leaks...

[Captaincademan Senior Member Find all posts View Profile Close Captaincademan]

Re: Any particular walbro pump?

Air leaks were the bane of my life for years, thats why I fitted a pusher. its 10 psi at the pump. add the restriction of lines, filters and height, and I imagine it comes back considerably. Not measured mind you. perhaps thats something I should look at.

All good points you raise JJ, but in my case I wanted for positive pressure in the fuel line, not increased performance. Ill take the performance lift though!

[Tim-HJ61 Donating Member Find all posts View Profile Close Tim-HJ61]

Re: Any particular walbro pump?

I am a little intrigued by the eagerness of many here to install pusher pumps on engines which already have their own lift pumps. These lift pumps mostly vane pumps built in to Bosch VE pumps by the factory are more than capable of drawing the fuel from the tank.

Hi JJ,

I agree with your observations, and many many times have tried to turn people off installing a pump that has to run all the time, when there are other passive means of increasing flow that are just as effective - such as increasing fuel line sizes. Your picture of the regulator is also a useful reminder. Just checking - these are on the outlet banjo of the IP aren't they??

However, as our experienced users have said above, there are several reasons why they have added pumps, and it works for them. In our WARFA group in Perth, we often get asked for what is going to work and at the moment I don't have a response other than 'try to not install a pump'. This isn't adequate, and some then fit a little square tick tick tick fuel pump, name obviously escapes me at the moment, and these are notoriously inadequate on anything but diesel, and maybe biodiesel. They make the problem worse.

Having a pump solution that I can pass on to others with some confidence is going to be helpful, no matter what purpose they want to use it for.

By the way, I have found that using IMG and /IMG tags around the photo makes it display in the thread, rather than using the link tag. It DOES have to be hosted externally though.

Tim

[Johnnojack Senior Member Find all posts View Profile Close Johnnojack]

Re: Any particular walbro pump?

Tim the regulator valve is in the top of the pump, often at the front on the side nearest the motor. Bueff it can be removed without taking the IP off or apart. The bad news is you need a modified socket to take it out. I used an old 3/8 socket modified with the angle grinder. The simplest thing to do is take it out and check the condition of the Orings. To set the pressure you need a pressure gauge connected to a fitting which fits where the outlet banjo is. The outlet Banjo is fitted back into the fitting. If you think this is beyond you, you could take it to a diesel mechanic and tell him you want the pump pressure checked, and if its not what it should be (check he knows first) then ask him to adjust the regulator valve. If he then spins a line about how the pump is worn out etc find someone else.
Tim I am also interested in a good pump to pump oil, but only to transfer it from my main tank to my oil tank as my main tank which holds 85 litres is only used for startup fuel and I could install another small tank for that.

[Johnnojack Senior Member Find all posts View Profile Close Johnnojack]

Re: Any particular walbro pump?

JJ,

If you are just after a reliable transfer pump - then grab one of the small gear pumps from Evilbay (or Scintex) - i have one that i use around the house and on trips to transfer from my travel tank to my main fuel tank - had it for nearly 4 years now and it has pumped thousands of litres and BIO and WVO and never missed a beat.

They are nice and compact and reasonably silent.

They do supposedly have a thermal cutout but even transferring a full 44 of oil i have never had it kick in.

Easy to wire into a switch on the dash and throw it when needed - they will run dry with no issues.

http://www.scintex.com.au/Pumps/SP12VGP14LPM-12V-Diesel-Gear-Pump/

It seems unlike everything else in the world - these pumps have actually gone up in price rather than down - now showing around the $160 mark - i remember they used to be all over ebay for around the $125 mark

Still good value

Craig

Thanks Craig I too have one of these, ditto about 4yrs use it on the road and 1000s litres. I was a bit shocked when I thought about getting a second one to find a lot of the sellers don't have them anymore and the one or two who do are asking more $. I reckon it is a bit big, heavy and would be hard for me to find somewhere to install one of these permanently on the vehicle. My vehicle tends to shake loose anything I fix to it as well. I might start another thread on fixing these actually.
For anyone wanting to check their pump pressure (IP) heres a pic of pressure take off.

[craigcurtin Senior Member Find all posts View Profile Close craigcurtin]

Re: Any particular walbro pump?

Yeah good idea re another thread - not sure what the underside of the jackaroos are like.

I have huge rails on my suburban so there are always plenty of places to bolt something to !!

Craig

[cuppatea Senior Member Find all posts View Profile Close cuppatea]

Re: Any particular walbro pump?

Agreed. I'm interested to know more about the pressure/regulator on these pumps. I often wonder what I should be checking/cleaning/replacing on my VE now that it comes in contact with VO.