TheSamba.com :: View topic - I Need Help with L-Jet / AFC Fuel Injection Topic

Sun May 27, 2012 10:30 pm

Colin suggested in a PM to swap injector from side to side and see if the problem followed and it may be a flow problem. Unfortunately it did not affect the situation.

We are out of ideas now. Im going to just keep cracking and re checking things but if anyone has a direction to push Id appreciate it.

Mon May 28, 2012 12:14 am

It is either electrical and one side is getting more voltage or a better ground so that the injectors work better, or the cylinders on the 3/4 side are getting air from another source that is downstream of the injectors such as cracks in the head or loose cylinders to head.

Another possibility if you still have the EGR valve is that that tube inside the plenum is partially clogged and as a result one side is getting more oxygen poor air than the other. If the EGR is still connected try blocking it with a piece of aluminum from a pop bottle at the filter. You can undo the two bolts (use a little penetrating oil on them first) then hold the pieces together temporially with two vice grips. if that isn't it then pull the piece of aluminum tin and tighten the bolts back up.

The EGR gasses have no oxygen in them as they are exhaust. They come out of a tube inside the plenum that has holes even,y placed in it so that ll the cylinders get an equal amount of inert gasses. The tubes plug up so that one side can get all the EGR gasses thus killing that cylinder(s) making them really rich while the others are lean.

Mon Jun 04, 2012 1:45 pm

I'm finally getting off my fat arse and have started working on the FI for the '78 Westy. The injectors are #0.280.150.100, 2.1 ohm 186cc @ 3 Bar. One of them is damaged from what looks like fire coming through a bad valve (tip is somewhat melted). I have a spare set of injectors # 0,280.150.114, 2.2 ohm 190cc @ 3 Bar. I talked to the fella @ Witch Hunter and was told there is no difference. Trying to cover my posterior can these be mixed together and work fine? should I stay with the injectors that came with the bus? Or can I use the spares? I'm new at this and trying to do it right. These are going into a new Adrian built engine.

Mon Jun 04, 2012 5:12 pm

the only real difference i am aware of is one style of injector has a removable hose and one doesn't.

Mon Jun 04, 2012 5:29 pm

The spares have braided hose and are shot. The '78s are solid hose and look good. I'm sure either hoses could be replaced (dremel through the compression fitting).

Fri Jun 08, 2012 4:29 pm

the plastic tips and internal screens are replaced when WitchHunter goes through them. Maybe they can sell you a set of tips. We sent ours to them and were pleased with the turn around and results. I actually sent 2 sets and then chose the best matched of the 8.

Sun Jun 10, 2012 2:41 am

SGKent wrote: MadFrankie wrote: SGKent wrote:

I do have one question that kind of puzzles me. You mention that it dies when you crack the throttle. Does this mean that you can start it anytime you want but all it will do is sit there and idle forever? Or are we seeing it start, idle for 10 -20 seconds and die at idle too? Can you start it anytime you try and then let it idle forever?

Hi,

Think that's the other poster whos having throttle problems. Mine has either worked perfectly or not at all.

Also, good point about introducing more potential problems. I'll hold off changing the points, plugs etc.

I think compression will be fine, it was last checked as part of me buying it back in June 2011. The reading was 120, 115, 115, 120

I'm guessing it will be the pump, it does seem that everything I do is leading towards it. I'll get the pressure gauge on it tomorrow, (any work got rained off today).

It will be the pump, ignition switch, loose wire, ground or one of the relays. I'd put money on that. Buses that work perfect then don't then do have something simple.

Hi guys, quick update on my situation.

After what seems like a year of rain and a backlog of work meanin little opportunity to get out on the van I think I've got it.

Borrowed my mates fluke multimeter to check my readings following the troubleshooting guide again and I've got sparks, power to and through the ecu and double relay but no pressure at all.

I've got power to the pump, (it actually read 17v when the engine was cranked), but no pressure which says faulty pump.

I did try putting a teaspoon of petrol in the s boot which didnt do anything different but I think I had fiddled with the lines and hoses a bit too much for anything to work anyway.

Going to get a new pump this week and fit it. Anyone got any final thoughts or comments as to anything I've missed?

Sun Jun 10, 2012 9:43 am

MadFrankie wrote: SGKent wrote: MadFrankie wrote: SGKent wrote:

I do have one question that kind of puzzles me. You mention that it dies when you crack the throttle. Does this mean that you can start it anytime you want but all it will do is sit there and idle forever? Or are we seeing it start, idle for 10 -20 seconds and die at idle too? Can you start it anytime you try and then let it idle forever?

Hi,

Think that's the other poster whos having throttle problems. Mine has either worked perfectly or not at all.

Also, good point about introducing more potential problems. I'll hold off changing the points, plugs etc.

I think compression will be fine, it was last checked as part of me buying it back in June 2011. The reading was 120, 115, 115, 120

I'm guessing it will be the pump, it does seem that everything I do is leading towards it. I'll get the pressure gauge on it tomorrow, (any work got rained off today).

It will be the pump, ignition switch, loose wire, ground or one of the relays. I'd put money on that. Buses that work perfect then don't then do have something simple.

Hi guys, quick update on my situation.

After what seems like a year of rain and a backlog of work meanin little opportunity to get out on the van I think I've got it.

Borrowed my mates fluke multimeter to check my readings following the troubleshooting guide again and I've got sparks, power to and through the ecu and double relay but no pressure at all.

I've got power to the pump, (it actually read 17v when the engine was cranked), but no pressure which says faulty pump.

I did try putting a teaspoon of petrol in the s boot which didnt do anything different but I think I had fiddled with the lines and hoses a bit too much for anything to work anyway.

Going to get a new pump this week and fit it. Anyone got any final thoughts or comments as to anything I've missed?

You could double cehck your theory by turning your ignition to on and nudging the AFM flapper with a pencil through the air box housing. If it is working you should hear the pump running, and fuel pouring back in the tank.

Sun Jun 10, 2012 7:35 pm

there are two wires to the pump. Make sure you are measuring voltage across the spade lugs which are part of the pump juat in case you have a bad ground wire.

Mon Jun 11, 2012 3:03 pm

H guys,

Tried the afm flapper at the weekend and nothing, not a peep from the pump.

I also checked the voltage across the 2 wires and got a reading so it looks like from my testings and from all your wonderful help that it's the pump.

Now to find one, rocking horse mess anyone?

Mon Jun 11, 2012 3:48 pm

vwheritage has some although the photo they show is one that has bolt on connectors so you will have to cut off the connector ends and crimp new ones on. I believe the original bosch unitswith spade style connectors can still be gotten through BusDepot in the USA.

Wed Jun 13, 2012 1:45 am

Hi,
if you do a search on samba for the VW fuel pump specs you'll start to come up with some alternatives, Ford Rangers (no use if you are UK though), Airtex E2000 (which I found on Amazon US so might also be available UK) and Bosch 69414 Original Equipment Replacement Elecric Fuel Pump, also on Amazon. There are quite a few alternatives, about £60 ish quid.

I think the key is to get a fuel pump that will deliver 60 psi. All the info I have found in the searches suggest that is the range. Then find a pump to match.

Theres going to be a regulator in there somewhere to ensure it doesn't put out too much.
Which does raise a Q in my head, does the regulator just limit it to a set amount. If you can find a pump to match that you will be sorted.

PG

Wed Jun 13, 2012 3:47 am

Actually a fuel pump just puts out volume, not pressure. It is the fuel pressure regualtor that does that part.

A good pump will deliver about 1L of fuel in 30 seconds.

Wed Jun 13, 2012 5:59 am

good point, Does that mean / or are you saying pretty much 'any' good fuel pump coupled with a regulator restricted to 60 psi ?

If that is the case thats quite useful to know, I have thought about my pump recently and what I would do if it gave up on me (I don't know its history or age).

I know regulators can be pretty generic, I have been trying to find one for a decent price for my carb based VW which would be as low as 2 psi but I have seen plenty of regulators are much higher (for FI) and also adjustable.

So that just leaves a half decent fuel pump that, at a guess, must be able to deliver min 60 psi, or as you say 1L of fuel in 30 seconds whatever that may be in pressure - which could also be a generic item. That widens the scope for what could be used without tying me up to hard to find/expensive/ages to get fixed.

Wed Jun 13, 2012 11:49 am

Two different fuel pumps we are speaking of....

A fuel injection pump is the one that puts out ~ 1L of fuel in 30 seconds. Normal operating pressure is <40 psi. The fuel pressure regulator limits the fuel pressure to what the engine actually needs, based on vacuum, and bypasses the rest (about 95% of the fuel pumped) back to the fuel tank. The fuel being pumped is what actually keep the pump cool. Also one of the reasons why a L-tronic never vapor locks.

So in a pinch, you could use a different fuel pump in the system. I guess.

A carb fuel pump stock puts out about 2-5 psi and generally has no regulator and doens't need one (unless you are running with certain dual carbs that like to see fuel pressures of <3.5 psi). On the factory mechanical pump you adjust the pressure by 1) using more gaskets on the base or 2) grind down the push rod that does the actual fuel pumping. A number of people use a electric "rotary pump" that is generally regulated internally at about 3.5 psi.

Edited to correct for my lousy typing. :oops:

Wed Jun 13, 2012 2:38 pm

That all really interesting as ive found a pump in GSF for £60 while heritage and the like are selling what looks like the same one at £250.

I did wonder if you could use a different pump from somewhere else but wouldn't know where to start as I've never had a bus with a FI system. It's a steep learning curve!

Thu Jun 14, 2012 1:14 am

FI is not too bad, different to my carb set up and with both being side by side I'd choose FI all day long. It is actually pretty straight forward once you get your head around it. (trust me, it blew me for a while but its quite clever when you realise although I still learn - re Q at end of this post !!)

As Randy correctly said, pressures are different between carb and FI (which i didn't make clear). I have ground my mechanical pump rod to get the right pressure for my carbs but I will still use a regulator for peace of mind, something like a malpassi/filter king/ sytec etc.

But back to FI, please share your experience with the pump, this was always a grey area to me but it seems a reasonably decent pump and a working right regulator (which you could buy an adjustable one) makes the options wider and lets be honest, £60 or £250 to do the same job is huge.

I never realised how inefficient it all is, up to 95% of fuel returned sort of begs the Q why so much but I guess thats needed to keep pressure high for the injectors.

I do have one more Q. the regulator looks to me like its on the fuel return back out the system but I would have expected to find it on the way in, i.e between pump output and fuel rail to injectors. I must have missed something there so bentley out time.

Cheers,
PG

Thu Jun 14, 2012 6:52 am

the regulator is like a dam at the end of the fuel river. the dam (regulator) has a leak in it, the size of the leak determines the pressure the regulator is holding. it's slightly variable with vacuum so that pressure is higher under load, this makes a richer mixture. the leak in the dam returns fuel to the tank. if the regulator was at the pressure side of the loop the pressure would be dropping all the way along as the injectors stole fuel from the loop. with the regulator at the end of the loop a constant pressure is possible since there is always more fuel than is required and most of it is returning to the tank through the controlled leak.

Thu Jun 14, 2012 7:50 am

what a excellent analogy Scott (acts like a dam), perfectly clear and another thing I have learnt/understood... which again makes sense. Maintaining the pressure behind it !!

:D

Mon Jun 18, 2012 12:09 pm

Hi guys - I am having a problem with my 78 2.0 FI:

I replaced the plugs, wires, cap, and rotor. I set my idle at 1k rpm, and my timing is in spec at 7.5*btdc and 28* btdc 3500rpm.

My problem is this:
I have a sputter/pop/backfire when I let off of the accelerator. It does not make this sound when I am on the throttle. It does not sputter/pop/backfire as much when I am stationary and press the throttle. The sound goes away immediately when I depress the clutch.

I've checked for vacuum leaks and I can't find any. Thoughts? Decel valve need to be replaced?

Thanks!