Ljet

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dingo
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Ljet

Post by dingo » Wed Apr 12, 2017 10:35 pm

78 2L Ljet: While cranking starter(and coil+ deactivated) fuel press goes up to 20, then when i stop cranking, swiftly drops to zero.
I clamped the inlet of fuel press Reg and cranked, fuel press goes off the guage*..haha..and i quickly stop, whereby the press stays at 40 and holds
Can i thus conclusde that no injectors are leaking, but PressReg is not functioning ?
There were no visible external leaks in the system.

* its a good way to test the veracity of all your screw clamps
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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asiab3
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Re: Ljet

Post by asiab3 » Thu Apr 13, 2017 2:27 am

I would be tempted to say you have found the root of your low pressure. Was the bus sitting? I have never heard of an FPR going bad unless the car sat for more than a year.

(For future tests, you can run the fuel pump by turning the key on and prodding the flap in the AFM. This way A) you won't wear out the starter, and B) you can hear the DR click and the fuel pump run (or not.) I like using my six senses in FI diagnosis.)

The sixth sense is the "voltmeter sense."
Robbie
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dingo
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Re: Ljet

Post by dingo » Thu Apr 13, 2017 9:41 am

Yeah, i coaxed the DR back to life and the flap now activates the pump. This engine did sit for a few years, so you are right about that.
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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dingo
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Re: Ljet

Post by dingo » Wed Apr 19, 2017 5:14 pm

OK, i finally have fuel pressure to spec. But the issue now is that there is no voltage at the injectors. I unplugged the connectors, cranked the starter and get 0 volts at the connector (manual says it should be intermittant 3 volts)
I checked the resistor pack..each one measures 6.5 ohms, and the incoming voltage is 12V with ignition ON. So that checks out.
Verified contniuity between Harness plug $1 and distributor trigger wire.
When i measure Ohms at the harness plug, i get 9 ohms per injector..which is the 6.5 of the resistor + 2.6 impedance at each injector.
I resoldered the 3 ground wire connectors...but i dont know if that has any benefit
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: Ljet

Post by asiab3 » Thu Apr 20, 2017 12:30 am

Start by following the essential current path:
- 12v at battery? (Duh, I think…)
- Battery voltage at pin #10 on the ECU plug, with the key on? (If not, then voltage at double relay 88b with key on?)

The injectors get their power from 88b on the DR, and current makes a stop at the resistor pack (series resistors) first. So if you have voltage coming out of the resistors, you probably have power at the injectors.

What manual wants an "intermittent 3 volts?" I am curious, as I can not find that in Bentley or the factory AFC training manual. Beware, though, that some ohmmeters are slow to respond. Your meter might not be able to sense the 2000 or more injector pulses per minute, so the needle or digital gauge might not move.

I find it easier to remove one bank of injectors and place each tip in a paper cup for cranking. (Plastic cups often melt.) Crank the engine over a few seconds, and shut off the key if it catches and starts to rev up. Look in the cups for fuel. It will be quaint in volume, but it will be there if the injectors are firing.

Robbie
1969 bus, "Buddy"
"Like a good sheep dog, it is ill-suited for show competition, only becoming beautiful when it's doing its job. It is a devoted servant, delighted with its lot in life, asking only that it be treated with the respect it deserves. You can't knock that."
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Re: Ljet

Post by Amskeptic » Thu Apr 20, 2017 10:04 am

asiab3 wrote:
Thu Apr 20, 2017 12:30 am
Start by following the essential current path:
- 12v at battery? (Duh, I think…)
- Battery voltage at pin #10 on the ECU plug, with the key on? (If not, then voltage at double relay 88b with key on?)

The injectors get their power from 88b on the DR, and current makes a stop at the resistor pack (series resistors) first. So if you have voltage coming out of the resistors, you probably have power at the injectors.

What manual wants an "intermittent 3 volts?" I am curious, as I can not find that in Bentley or the factory AFC training manual. Beware, though, that some ohmmeters are slow to respond. Your meter might not be able to sense the 2000 or more injector pulses per minute, so the needle or digital gauge might not move.

I find it easier to remove one bank of injectors and place each tip in a paper cup for cranking. (Plastic cups often melt.) Crank the engine over a few seconds, and shut off the key if it catches and starts to rev up. Look in the cups for fuel. It will be quaint in volume, but it will be there if the injectors are firing.

Robbie


Let's tighten this up. There are no 2,000 injector pulses per minute at cranking or idle.

Dingo, pull an injector plug. Turn on ignition. Put your test light alligator clip on a good metal ground. Lightly contact either of the two terminals in injector plug. Find which of the two terminals lights up. That is the 12 volt side (actually about 7 but whatever). The other side is the ground path to the ECU.

TO TEST GROUND SIDE - you need to put your test light alligator clip to the (+) #15 on the coil, the probe on the ground side of the injector plug and crank engine. This is where you should see pulsing.
Colin
BobD - 1978 Bus . . . . . . . . . . .110,334 miles
Chloe - 1970 bus . . . . . . . . . . .191,387 miles
Naranja - 1977 Westfalia . . . . 72,350 miles
Pluck - 1973 Squareback . . . . . 55,560 miles

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Re: Ljet

Post by dingo » Thu Apr 20, 2017 10:11 am

OK thanks, i will try all that today

( asiab3: I was going by page 23 A.F.C. online manual...tho i was using a meter not a test light)
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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dingo
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Re: Ljet

Post by dingo » Thu Apr 20, 2017 12:52 pm

On injector plug #1 and #2, with IGN ON..i get 12V at BOTH terminals of the plug. Between the two terminals there is 10.6 ohms with harness plug plugged in, and No continuity when unplugged.
ok, so when resistor pack unplugged..i lose the 10 ohms, and there is no continuity between terminals.
Neither terminal of connector shows any connection to GND at any time
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: Ljet

Post by dingo » Thu Apr 20, 2017 3:07 pm

ok...in between incessant rains...pulled injector plug 3 and 4...and they both have 12V on only one terminal and nothing on the other...so some normalcy on the 3.4 side

edit: if any single injector plug is connected, then ALL of them will have 12v on BOTH on both sides (in once case 10V)
if ALL injector connectors are unplugged are removed, then ALL plugs show 12V on one terminal and 0v on the other, as is supposed to be normal


-wih all connectors unplugged, meter between coil+ and the injector plug Gnd terminal, i crank and get flickering of 4-6 v...assume this is correct function...so with electrical seeming to function, on to visual..

-spray test yields NO spraying...just a drop or a whiff of gas...could it be all four injectors are gummed up ?

thats where im at
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: Ljet

Post by dingo » Fri Apr 21, 2017 11:16 pm

Handy DIY injector cleaner: attach foot long hose to injector, then fill with whatever cocktail of choice..then pressurize that fluid using the pos. pressure side of a Mighty-Vac hand pump..pump afew times, it holds the pressure on its own..then trigger the injector using a toggle swithc and a 6v power supply...watch the spray pattern in a clear plastic cup...repeat if neccessary.
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Re: Ljet

Post by Amskeptic » Sun Apr 23, 2017 5:08 am

dingo wrote:
Thu Apr 20, 2017 3:07 pm
ok...in between incessant rains...pulled injector plug 3 and 4...and they both have 12V on only one terminal and nothing on the other...so some normalcy on the 3.4 side

edit: if any single injector plug is connected, then ALL of them will have 12v on BOTH on both sides

-spray test yields NO spraying...just a drop or a whiff of gas...could it be all four injectors are gummed up ?

thats where im at


Don't go distracting yourself with gummed up injector speculations just yet. You have a 12 volt source killing your injector grounding. Can't be too good on the ECU either. Check wiring! Is the ECU signal wire from the coil on the negative side #1 (-)?
Colin
BobD - 1978 Bus . . . . . . . . . . .110,334 miles
Chloe - 1970 bus . . . . . . . . . . .191,387 miles
Naranja - 1977 Westfalia . . . . 72,350 miles
Pluck - 1973 Squareback . . . . . 55,560 miles

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dingo
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Re: Ljet

Post by dingo » Sun Apr 23, 2017 10:27 am

Yes signal wire to #1 on ecu goes to #1 on coil (-)....
My theory on the 12V at gnd terminal of plug is that....unless you remove all four connector plugs at the same time..then 12V goes thru the 6.5 ohm resistor pack, thru the 2.6 ohm injector and into the inj.ector gnd circuit..and appears as 12v
Since all four injectors are fired simultaneously, then all 4 pos terminals are interlinked, as are all 4 gnd terminals
i dont know if that makes sense

also..if i measure voltage going into resistor pack, its 12V..and immeadiately after resistor pack is still 12V...i assume that it only drops to 3 0r 5v, when under load of the solenoids being actuated...

I could not un-gum the cs injector...a variety of solvents...so i pried it open to find a dissapointingly crude device..like a childs toy...there was no gum..the solenoid clicks but...could not discern why the plunger and spring do not retract...anyways i dont see how i can reglue this back and hope to contain 40 psi without the common weeping between plastic and metal can
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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Amskeptic
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Re: Ljet

Post by Amskeptic » Mon Apr 24, 2017 5:40 am

dingo wrote:
Sun Apr 23, 2017 10:27 am

Since all four injectors are fired simultaneously, then all 4 pos terminals are interlinked, as are all 4 gnd terminals
i dont know if that makes sense
(+) to injectors through series resistors, test lamp should light on that side of injector plug.

(-) to injectors is provided solely by the ECU through four discrete channels

Work this anomaly out.
Colin
BobD - 1978 Bus . . . . . . . . . . .110,334 miles
Chloe - 1970 bus . . . . . . . . . . .191,387 miles
Naranja - 1977 Westfalia . . . . 72,350 miles
Pluck - 1973 Squareback . . . . . 55,560 miles

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Re: Ljet

Post by sgkent » Mon Apr 24, 2017 9:21 am

(Except on 1979 and later California). The relay provides 12V+ to the 4 ballast resistors. Their purpose is limit amperage to the injectors. The ballast resistors each have a wire that goes to one injector. When the key is on the injectors will have 12V+ to them. The ground side of each injector goes into a common harness that goes to the ECU. The ECU provides a pulsing ground to all four injectors simultaneously. The ECU receives a pulse from the ignition coil primary on the distributor side (#1) through the signal wire. The ECU then electronically (analog) reshapes that pulse into a square wave that is used to ground the injectors as described above. One of the easiest methods to test the system is to buy an inexpensive NOID light off Amazon, Summit Racing, or Ebay etc. I think I paid less that $10 for mine shipped. It is plugged into the injector connector and it will flash each time the injector would have fired. If all four connectors flash properly then the only reason the injectors aren't working would be they are bad or have no fuel pressure.
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dingo
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Re: Ljet

Post by dingo » Mon Apr 24, 2017 3:45 pm

With all 4 inj plugs disconnected.....IGN ON..each plug has 12v and 0v
- all pos terminals are interconnected to each other
-all gnd terminals are inerconnected (full continuity) to each other

when i have ign on, i get 12v at coil+ Primary and also 12v at coil(-) secondary...this is with all other leads disconnected. is this normal ? Coil+ to Coil- is 3.6 Ohms.... + to tower 8.7k, same for -

just got a test light..so ill do nthat next

Ok, test light plugged into injector plug, i get nothing..nada no flickering..same with all plugs whether plugged in or not

Final test of the evening: per Bentleys F.I. page 20 'Ohmeter test "there should be no electrical continuity between each of theterminals inside the four injector plugs, and the chassis(ground)"
So the results of this were: No Continuity for 1 terminal and 50k ohms for the other..this was the same for each of the 4 injector plugs.
So the 50k...? thats when i had to quit for the day
'71 Kombi, 1600 dp

';78 Tranzporter 2L

" Fill what's empty, empty what's full, and scratch where it itches."

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