Tristan smith
Low Mileage
I am looking to replace the factory inline fuel pump with something like a walbro 255 and a adjustable regulator but I'm not sure what the proper factory fuel pressure. Some assistance would be greatly appreciated
Fuel pressure on stock fi 1500cc
- Thread starter Tristan smith
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- fuel injection fuel pump
Brad Garska
True Classic
The Manual states 33-39 psi
Edit I should have been clearer. System pressure is as stated above however the fuel pump alone is rated for 39-45 psi
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Tristan smith
Low Mileage
Thank you much
Dr.Jeff
True Classic
Tristan, keep in mind increased pressure is a function of reduced volume. To increase the pressure, a resistance must be added to 'back up' the flow and create head (that's what the pressure regulator does). So be sure any pump you choose has sufficient flow capacity to make the needed pressure. Walbro pumps seem to be good, I'm not familiar with their models (does 255 stand for L/hr or such?). For these engines it isn't to bad; under 40psi really isn't that high of pressure. So I'm sure it will be fine, but just something to make sure of before spending the money. Typically pumps are not returnable so I'd hate to see you get stuck with something that won't fit your needs. 
ng_randolph
Bjorn H
Keep in mind that L-Jetronic does not keep a constant fuel pressure, but rather a constant difference between fuel pressure and plenum pressure. L-Jetronic relies on this for proper fuel metering, so whatever new regulator you put in should do the same thing.
lookforjoe
True Classic
Tristan, keep in mind increased pressure is a function of reduced volume. To increase the pressure, a resistance must be added to 'back up' the flow and create head (that's what the pressure regulator does). So be sure any pump you choose has sufficient flow capacity to make the needed pressure. Walbro pumps seem to be good, I'm not familiar with their models (does 255 stand for L/hr or such?). For these engines it isn't to bad; under 40psi really isn't that high of pressure. So I'm sure it will be fine, but just something to make sure of before spending the money. Typically pumps are not returnable so I'd hate to see you get stuck with something that won't fit your needs.
While this is true, pumps used on Bosch EFI start with a line pressure much higher than required at the rail, so the regulator bleeds off at least 50-60% of the flow back to the tank at any given moment. Typical line pressure for a Bosch pump used here is around 80 psi.
Walbro quality can be spotty, and there are many cheap KO versions to be avoided.
My concern would be where and how (and why, actually) you plan to add a regulator - since there is already on on the rail. You have to have a return type regulator, not one of the (cheaper) returnless type. This would also mean reworking the stock fuel rail, since the existing regulator is an integral component.
EDIT: I reworked my setup using Volvo parts - lines & regulator from an old V70, to eliminate all the extra return side plumbing. Also allows me to use a wider range of fuel filters. Use quick release fittings. VW/Audi also used this design, so I was able to use an adjustable regulator that inserts into the 'pod"
To do something like that with a stock fuel rail would mean making an adaptor fitting for the flare line fitting, and eliminating the stock regulator at the other end of the rail.
Adjustable regulator is the blue pod..
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Dr.Jeff
True Classic
Good point. Many of the aftermarket pressure regulators do include a vacuum port connection to do this, typically referred to as raising rate regulators. The adjustment aspect allows you to set the base pressure at idle, then the vacuum signal adjusts that pressure with load changes. Not all regulators have the same rate of change for the vacuum signal, which can be used to increase mixture at a different rate if desired (by selecting a regulator accordingly).
Well stated. That was the point I was trying to make about the replacement pump having enough flow volume capacity to allow for the pressure needed.
Tristan smith
Low Mileage
Sorry not trying to sound ignorant. This is a learning experience for me. But I appreciate the information
Tristan smith
Low Mileage
Could you send an image of the upper right hand corner directed to the coil and ignition control. I seam to have some wires that are miss placed and I'm trying to piece it together
Dan Sarandrea (Phila)
Waitin' On Parts...
In case you haven’t seen it, there is a copy of the factory FI guide in the wiki.
http://xwebforums.com/wiki/index.php/FuelInjectionTroubleshooting
lookforjoe
True Classic
I haven't had a stock setup for 10 years, so I'm not help in that regard. There are pics of stock setups if you search the forum.
Post a pic of what you have, will likely be easier for us to explain what you have & what may be amiss to you, rather than post a pic that you may or may not understand.
The three components you should have on that inner right panel are the coil, ballast, and on the outer side, the ign module.
EDIT: Found an old pic from when I still had L-Jet. You can see the coil & ballast location. Ignore the grey cube on the coil bracket, that is just a suppressor.
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Hi Tristan,
I am a little late with the pictures, but here are some I took of my 86.
The following pics show the thick wire with the piggy back connector. If it falls off the coil, the engine will crank forever and never fire. It takes a while to spot the problem because with the piggy back being in the middle, it makes the wire look "whole" and not an obvious disconnected end. This may not be your problem, but it is good to be aware of. I have "fixed" a couple in-op Xs by reattaching this wire. It is not hard to knock it loose when reaching down into that area working on plug wire, etc. I know this the hard way.
I am a little late with the pictures, but here are some I took of my 86.
The following pics show the thick wire with the piggy back connector. If it falls off the coil, the engine will crank forever and never fire. It takes a while to spot the problem because with the piggy back being in the middle, it makes the wire look "whole" and not an obvious disconnected end. This may not be your problem, but it is good to be aware of. I have "fixed" a couple in-op Xs by reattaching this wire. It is not hard to knock it loose when reaching down into that area working on plug wire, etc. I know this the hard way.
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