1986 Vanagon Troubleshoot
June 12th, 2012
In early May 2012 my1986 Blue Vanagon had had several instances of a seemingly random “miss.” It would, while just running normally, seem to misfire, but only a very short time. It was at first hard to tell the difference between a small barely perceptible jolt in the road, say from a small twig or rock or small bump than the engine misfiring. It did this several times. Toward the end, it did this for half a second or maybe once or twice two seconds but always picked back up fine with no action from me.
I always figured to do a tune-up but the problem surely seemed to be extremely intermittent.
Finally at 11 p.m., while coming home – it quit totally with no warning at all. Had to pull back home the next morning. While cranking to try to start, I could smell gasoline, so thought the problem was no spark. Also, it did try to catch a couple of times, and when it did, ran with no power and had blue smoke.
At home, it has run sometimes, if you would call it running, but with no power and always stalled right away (maybe 2 seconds with a ramp down in power til it stopped and usually would not fire again.
I removed the spark plugs and replaced them with new ones. The old ones did not appear bad, - not oily, few deposits at all. The compression was indeed low all around. I attributed this to the gasoline smell and cranking the engine a lot washing the oil off the rings. Did not do a wet compression check due to the difficulty of accessing the spark plug holes. Readings were 70-90 pounds.
On 11 June I started troubleshooting with the manual in earnest. At first the fuel pump; would not run at all. The relays would energize when removed and when checked with a DVM, seemed fine. The Number I relay seemed to not want to energize. I removed the cover to inspect it but it seemed fine.
After unplugging the control unit, and doing checks 1, 2 and 4, and plugging back in, with the ignition carefully OFF while unplugging, the fuel pump; has worked fine. You can hear it work for a short time every time the ignition is turned on. The, apparently when the regulator senses adequate fuel pressure, the audible humming is no longer heard. Before plugging and unplugging the Control Unit, I did not hear this. There may have been a poor connection of the Number II fuel pump; relay or a bad input form the control unit. Did both close in time. When the Control Unit was plugged back in, that was when the fuel pump; started working.
I did the flow check for the fuel pump per the book instructions on page ______and the fuel flow is OK.
11
Check of the Control Unit are as follows:
CONTROL UNIT = Bosch
0 262 200 065
Page 24.61 Electrical Testing –Ignition and Injection System
TEST STEP / (CONNECTOR)
TERMINAL / TO TEST / Additional
Conditions / Specified Values
1 / 13 + 14
14 + 19 / Control Unit Voltage Supply / Switch Ignition ON / Approx. Battery Voltage OK
2 / 13 + 25 / Wire to Ignition Coil Term. 1 / Switch Ignition ON / Approx. Battery Voltage OK
3 / 1 + 13 / Wire from starter Term 50 ;and from adapter for idle stabilizer control unit terminal50 / Disconnect connector from injectors; Operate starter (in Neutral) / Minus 8 volts
(can’t check due to not having VW adapter)
4 / Bridge 3 + 13 / Wire to F.P. relay / Ignition switched ON / F.P must run audiblyIT DOES
REQUIREMENTS: IGNITION SWITCH OFF;
Measuring Range: Resistance Measurement Ω
5 / 12 + 14 / INJECTORS / Connect ONLY ONE Injector at a TIME !!! / 15 – 20 ΩYES
6 / 6 + 10 / Temp Sender for Engine Temp / ------ / See diagram on 24.45. (at 50 deg F = 3000 – 4000 Ω
Decreases above 50 deg. OK
7 / 6 + 11 / Throttle Valve Switch / Throttle Valve Closed: / CONTINUITY
OK
Slightly Open to shortly before Full Throttle / ∞ Ω OK
Completely Open / Continuity OK
8 / 6 + 17 / Intake Air Sensor Potentiometer / 0.5 – 1.0 KΩ
OK
17 + 21 / Move Air Flow Sensor / Change In
ResistanceOK
9 / 6 + 9 / Intake Air Temp Sender in intake air sensor / See diagram p.24.45 (At
10 / 6 + 8 / Wiring to Hall Sender / Remove connector from Hall sensor and bridge all 3 connectors / Continuity OK
6 + 18
11 / 2 + 13 / Wiring to Oxygen Sensor / Disconnect connector to Ox Sensor and hold green wire to ground / Continuity OK
Re-connect wiring / ∞ Ω Didn’t do
NOTE: For additional tests of the Digifant System as well as the Hall Sender test see Repair Group 28
From Page 28.43, the OUTER TERMINALS of the Hall Sender (At Distributor) should read minimum 10 volts. (Ignition ON – Connect DVD – Switch Ignition back OFF
IF NO – Replace Control unit This was Ok at 11.18 volts
The HALL Sender is likely good due to the flickering of the spark plug tester when in series with BOTH the coil wire at the distributor and the individual spark plugs.
INTAKE AIR SENSOR – CHECKING (Page 24.57)
Remove connector and hose from intake air sensor and test with DVD. Using VW Adapter 1315A/1.
-Potentiometer checking: Term 3 – 4 = specified value approx 0,5 – 1.0 KΩ
-Move air sensor flap + check resistance betw Term 2 + 3 = RESISTANCE CHANGE
(Both the above readings were OK)
INTAKE AIR TEMP SENSOR CHECKING, page 24.57
Measure Resistance between terminals 1 + 4. 68 deg. F (20 deg C) = 2.3 -2.7 KΩ
Over 68 deg=Ω Less
Under 68 deg.=Ω More
Above were OK
P28.44 – Checking Ignition switch function from Control Unit. Terminal 1 + 15 of ignition coil; Disconnect Hall Sender – Ignition ON –Hold center wire of hall sender connector to GROUND. Should read approx 4.5 volts. IT DOES. 4.7VDC.
P24.53 Idler stabilizer; 1st check: engine not running. 2nd check = OK= Continuity( 4.5 Ω)
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