D-Jet head temp sensor question Options

[Joe Bob]

Anyone have the specs on the resistor that is used on the 74, 2.0 head temp sensor? I have a lean condition and need the sensor....how many ohms?

[TravisNeff]

You add resistance to lean out the mixture. Only the 73 used a resistor. 270 Ohm.

[Joe Bob]

Not according to the Krusty one....it's lean, and he says he needs one to fatten it up. Specific to the 74.....

[TravisNeff]

Hmm. Here's a snippet from Brad's Djet page. Resistance goes down as the engine warms up, and in my head the mixture would lean out as the engine is warm. As for a resistor for a 74?? Never heard of one.

Normal Value(s):
0 280 130 003 and 0 280 130 012: about 2.5 K ohms at 68 deg. F, less than 100 ohms with hot engine.
0 280 130 017: about 1.3 K ohms at 68 deg. F, less than 100 ohms with hot engine.

I am wrong, here's the data on the resistor, cept' that it is only for 1973.

Function: Biases the resistance of the head temperature sensor across the entire temperature range to cause the ECU to provide a overall richer mixture. Only used on 1973 2.0L's.
Normal Value(s): 270 ohms
Failure Modes
Open: Same effect as an open head temperature sensor (see above). Check with an ohmmeter.
Shorted: Eliminates bias from head temperature sensor. Causes leaner mixture across full range of operation, resulting in drivability problems, possible backfiring. Check with an ohmmeter.
Mismatched or wrong value: Many owners are aware that using a resistor to bias the head temperature sensor is a way of affecting the overall mixture of the D-Jetronic system. Depending on the value used and the setup, you can end up with a lean or rich mixture. Using a bias resistor other than as specified for the 1973 2.0L is only suggested when there is no alternative to obtaining good drivability.
Notes: Used only on the 1973 2.0L engines in the combination of components described above in the cylinder head temperature section. It is used to bias the resistance of the 0 280 130 017 cylinder head temperature sensor. Since the ...017 sensor has a cold resistance value of about 1300 ohms, and a warm value of less than 100 ohms, use of the ballast resistor increases the value the ECU sees at both extremes by 270 ohms. If this resistor is missing from a 1973 setup, the mixture will be too lean across the whole temperature range. Use of this resistor in a 1974 setup will result in a rich mixture when the engine is warm. Make sure that if you have a 1973 setup as described above, that this resistor is present, and if you have a 1974 setup, that it isn't installed.

[toon1]

At what point are you lean? during W/U or at operating temps?

How do you know you are lean? AFR gauge?

[Joe Bob]

When warm at idle it goes lean. Brain knob is all in at full rich.

Krusty's "nose" tells him it's lean....

[Joe Bob]

As rare as they go bad....I'm leaning toward the ECU being the culprit.

http://members.rennlist.com/pbanders/DJetParts.htm

Per Brad Anders site....the 73 was the one that had a ballast resistor.....

So...yes, Travis you were right. (IMG:style_emoticons/default/pray.gif)

[markb]

Checking the pbanders site, the 74 2.0 had a different sensor than other years. Maybe this is the culprit?

[r_towle]

go buy a POT and put it inline. one that goes from 0-1000 ohm..
set, test, set, test...when its right, remove the POT and measure it with an ohm meter, then go buy the right resistor.

Both can be had at radio shack.

Rich

[Bleyseng]

Checking the pbanders site, the 74 2.0 had a different sensor than other years. Maybe this is the culprit?

only the 73 2.0L had a different CHT the 017
all other years including ljet buses use the 012 CHT.

full CW at idle?? sumthin else is wrong...wrong ECU?? should be 044 for a 74.

[toon1]

When warm at idle it goes lean. Brain knob is all in at full rich.

Krusty's "nose" tells him it's lean....

As rare as they go bad....I'm leaning toward the ECU being the culprit.

http://members.rennlist.com/pbanders/DJetParts.htm

Per Brad Anders site....the 73 was the one that had a ballast resistor.....

So...yes, Travis you were right. (IMG:style_emoticons/default/pray.gif)

If it's warm and lean I would guess it's NOT the CHTS. when the engine warms up, the ECU ignores the CHTS.

NOT doubting Krusty, but how do the plugs look?

What about bumping the F.P.?

[TravisNeff]

Dirty-clogged injectors? My 1.7 djet has the same issue. During my emissions test I passed with flying colors on the loaded tests (all 5 of em) and failed for idle hc due to it running lean at idle. Like you I had set the ecu to full rich to pass and it only did by 3 points. No vacuum leaks and all the parts check out except for low compression on a couple of cyls. So my thinking it could be compression or clogged up injectors

[davep]

http://www.914world.com/bbs2/index.php?showtopic=84088

[markb]

From Paul Anders' site:

Cylinder Head Temperature Sensor

311 906 041 A

0 280 130 003 1.7L 1970 - 1973
0 280 130 012 2.0L 1974 - 1976

Discrepancies: The PPC lists this Porsche/VW part number for the engines below. The BGDIP cross-references this VW part number to the 0 280 130 003 sensor, which is the sensor for the 1968-1969 Type 3's. I checked with my local Bosch supplier and the ...003 is the part he found for this Porsche/WV number . The DSM lists the 0 280 130 012 sensor for these engines and years, but not for the 1974 2.0L. Note that the 0 280 130 003 sensor is used by some 914 owners to get a richer cold engine mixture.

W0 000 001 => W0 250 000
EA0 000 001 => EA0 098 793
EB0 000 001 => EB0 009 703
GA0 006 766 => GA0 015 021
GC0 000 001 => GC0 006 946

[jasons]

go buy a POT and put it inline. one that goes from 0-1000 ohm..
set, test, set, test...when its right, remove the POT and measure it with an ohm meter, then go buy the right resistor.

Both can be had at radio shack.

Rich

(IMG:style_emoticons/default/agree.gif)

I have a 73 with the the 270 ohm resistor. My FI is almost completely refurbed. When I got it running, it had the lean idle hunt. I went to the Shack and got a variable resistor 0-1000 ohm and replaced my 270 ohm with it. I dialed it up until the lean idle hunt went away. I wound up at 480ohms I think. I also checked this on an exhaust gas analyzer, and I passed AZ emissions with this setup. So, I know it worked for me.

It may not be your problem, but for $3 or whatever the variable resistor costs, its an easy try.

[Joe Bob]

yep...I found that same variable resistor....I seem to remember having to do this as well back in the 80s. DejaVu all over again.....

[Joe Bob]

Spoke with another friend of mine...factory trained wrench from back in the "day"....suggested that the MPS adjustment would be better. Not that I'm, a D-Jet whizz......far from it. I mostly did carbs and cams when confronted with a T1 or 4 motor, more power, grunt, grunt, etc. Stock always equaled "loser" in my book.....things change, right? (IMG:style_emoticons/default/dry.gif)

BUT, I DO remember that futzing with the MPS by taking off the epoxy on the back and adjusting it was always the sign of a "boogered up" system.

COMMENTS?

[jasons]

Do you have the right match of FI parts? If you haven't done so, I would verify all the part nums (ecu,mps,sensors, etc) on Anders site. Playing with the MPS on a stock motor sounds like the last resort. No luck with the resistor?

[Joe Bob]

Haven't had the chance to try it. The '14 is at Krusty's, 80 miles or so north.

It just got out of the alignment shop and the resistor is in my pocket. So....I'll be cruising up soon as John gives me the "sign"......

I was just curious if anyone ever did the MPS thing....I won't try it unless it's a last resort. I'm tring to keep it ALL stock.

The engine had a gas leak and fire.....the PO boogered the wiring to fix it. What temp sensor is on it, I don't know......the addition of the resistor seems the least invasive/bandaid of a fix. Obviously the best idea to install and then stick a probe in the tail pipe and see how it runs, cold/warm idle and then at 2500 rpms....

[r_towle]

Spoke with another friend of mine...factory trained wrench from back in the "day"....suggested that the MPS adjustment would be better. Not that I'm, a D-Jet whizz......far from it. I mostly did carbs and cams when confronted with a T1 or 4 motor, more power, grunt, grunt, etc. Stock always equaled "loser" in my book.....things change, right? (IMG:style_emoticons/default/dry.gif)

BUT, I DO remember that futzing with the MPS by taking off the epoxy on the back and adjusting it was always the sign of a "boogered up" system.

COMMENTS?

If it had a fire, I would suspect all the sensors.
The MPS could be leaking, or it could have gotten to hot inside and futz up something.
The ECU could be the same situation.

Krusty is the man...make him figure it out,...or are you being a CSOB...
One thing to test, if he has the Bosch FI tester, it checks every sensor, and validates all the wiring and proper settings of each sensor.

The tests probably would take no more than an hour or two and it also checks the ECU...so its probably a good way to start ruling out the ECU and faulty sensors.
It does check the electrical functions on the MPS...not the vacuum...but the vacuum is what you change when you turn the screws...the elec needs to work for that to have any affect.

Rich