w114 no start - PeachParts Mercedes-Benz Forum

kunbarrie · #1 03-20-2015, 12:40 AM

hi all a w114062 280e 110 eng jettronic injection system,has no injector pulse,all tests on mercedes test sheet ok,trigger pulse good,map sensor primary and secondary circuits and earth ok,wireing ok as all test results are at factory specs,have tried a ecu from a running car ,still no pulse,any ideas at all thanks.

meltedpanda · #2 03-20-2015, 01:35 PM

Djet system

All resistance checks must be conducted with the ignition off.

Injectors:
Individually check ECU harness pins 3, 4, 5 and 6 to ground. Resistance should be less than 25 ohms, but not zero. NOTE: The ECU powers the injectors with a 3V signal lasting between 2 and 5 milliseconds. This signal cannot be measured with a meter; don't try.
Trigger Points:
ECU harness pin 12 to 21, then pin 12 to 22 = near 0 ohm continuity on one set, open on the other. Rotate engine 360 degrees and test again. Readings should be opposite.

and I suspect you have checked all fuses and fuel start relays?

kunbarrie · #3 03-20-2015, 10:04 PM

yes have done all that,cannot fault electrically,have found pressure sensor not holding vaccuum,could be mechanical fault in pressure sensor even though all resistances are ok,

Frank Reiner · #4 03-20-2015, 10:39 PM

Quote:

Originally Posted by kunbarrie

hi all a w114062 280e 110 eng jettronic injection system,has no injector pulse,all tests on mercedes test sheet ok,trigger pulse good,map sensor primary and secondary circuits and earth ok,wireing ok as all test results are at factory specs,have tried a ecu from a running car ,still no pulse,any ideas at all thanks.

If no injector pulse, using two different ECUs, one of which is known good, one would be inclined to pursue Der Panda's question about fuses, i.e., is power actually reaching the ECU?. In W114 D-jets the power is supplied through a main relay for the injection system; it is not fused on the power circuit, but is fused on the energizing circuit (#5).

cth350 · #5 03-21-2015, 10:38 AM

Do you have the M110 d-jet schematic rather than the v8 one?
Also, the older M110 service manuals have section 7.4 with the necessary instructions. Newer copies don't have it.

-CTH

kunbarrie · #6 03-22-2015, 04:46 PM

pin 11-16 and 11-24 voltage supply for computor given value 12v
pin 11-18 voltage from starter motor term 50 9.5v
pin 11-19 connected electrical system of fuel pump pump rotates.
all ok.

Frank Reiner · #7 03-22-2015, 06:08 PM

kunbarrie:

If you are indeed confident about the power supply, look now to the ground (earth) connection of the injectors. All six are in parallel, and share a common, single point connection, typically to the cylinder head. With an ohmmeter, check the brown wire terminal in each injector plug (first unplug all six). The plug ground terminals should show 0 ohms resistance to ground. The screw, and the eyelet of the ground wire may be corroded at the point of contact on the head. Similarly, ensure that the ECU harness ground (pin 11) is also clean, and has 0 resistance. All body and engine grounds must also be common with the battery ground. Ground faults, while seemingly obvious, are overlooked rather often.

meltedpanda · #8 03-22-2015, 08:04 PM

2nd what Frank is saying.
Also
Do you have spark, ( plug out grounded and you can see it ) ?

air- fuel -spark- gotta be one of the three
Have you determined that in the distributor the rotor is indeed at cyl 1 when it is suppose to be there?

kunbarrie · #9 04-01-2015, 01:03 AM

fixed problem,fault was in the common injector wire earth,the connector was clean and tight,problem was the crimping on terminal was not tight enough,re crimp and car runs ok thanks all.

meltedpanda · #10 04-01-2015, 11:22 AM

good ! Like I said - had to be one are all of three - air- fuel- spark