input needed for no start

[A horse with no name]

Update...

When grounding #20 on the harness the fuel pump should run but it doesn't.

There is though 12+ volts at #1 on the ECU harness.

At the speed sensor harness there is .9877 ohms ( should be from .6 - 1.6 ohms )
On pins #8 and 27, on the harness, the reading is the same so the new speed sensor is working.

When I manually let the fuel pump run, there was no smell of gas anywhere. When I loosened the fuel plug on the left injection rail there was pressure.

[ischmitz]

Looks like this is continued here: DME relay - No can jump.

[A horse with no name]

Originally Posted by ischmitz

Looks like this is continued here: DME relay - No can jump.

Yes, I am sorry to say but it is. I was actually going to drop you a PM as I have read many of your posts on these matters over the years. They have been very good. .

Being that the DME(s) relay is not working, I guess that I should purchase another one. As mentioned, the original one worked; I have carried this new one in the car as a spare...Would you be able to provide me with any info that you may have regarding why I can not get the pump, and the secondary set of points, to work when jumping the three pins of 87-87b and 30?

[A horse with no name]

Where I am at the moment...

I have 13 V on the #30 female pin of the DME. I have tried both; the one I took off and the new spare that I have. (both covers are of). I can get the pump to run if I manually hold the points for the pump, but I cannot get it to run when jumping #87 -#87b and #30.

When grounding #20 on the harness the fuel pump should run but it doesn't.

There is 12+ volts at #1 on the ECU harness..

At the speed sensor harness there is .9877 ohms ( should be from .600 - 1.600 ohms )
When testing the ohms on pins #25 and #26, on the connector harness, the reading is the same, so the new reference sensor is working. The speed sensor, pins #8 and #27, also had similar reading so it is also OK.

When I manually let the fuel pump run, there was no smell of gas anywhere. When I loosened the fuel plug on the left injection rail there was pressure.

Any idea's?...

[A horse with no name]

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Let's try to get some clarifications on record here:

DME: Is the large box with silver metal cover under the driver's seat and is also called ECU or control module or similar. It is the electronic brain that "listens" to the sensors and delivers fuel and spark signals.

DME relay: is the black small box. It's a double-stage relay (or two relays with some common connections) that serves two purposes.

DME relay stage 1 is where a portion of Term#15 is controlled. This is the branch that is powered when the ignition is in RUN or START. This stage turns on and then powers the injectors and the ICV and the DME itself when you turn the key. It also provides power to the positive side of the coil of relay's 2nd stage.

DME relay stage 2 of the DME relay could also be called fuel pump relay since it serves exactly that function. It is controlled by the DME and when it is turned on it powers the fuel pump and the O2 sensor heater.

Term#30 on the DME relay socket is a direct connection to the battery positive terminal without fuse. So this should always be +12V.

Pin 20 of the DME harness needs turn the 2nd stage of the DME relay on only when the key is in RUN position. If that doesn't work the DME relay or the harness is damaged or the ignition switch isn't working. Could also be an alarm issue if equipped.

Pin 18 and pin 35 are connected internally inside the DME harness. The wires are spliced together inside. If you are absolutely sure you have counted the pins correctly this would suggest the DME harness is damaged. A very unlikely but not impossible scenario.

The resistance readings are 800 - 1600 Ohm or 0.8 - 1.6kOhm. Same difference but let's keep the units correct if someone else reads this in the future.

Let me ask you this: When you turn the key to RUN you should see (if the cover is off) and hear the DME relay click. This is the first stage turning on. At the same time you should confirm that the ICV on the back on the engine is vibrating. That tells you that the DME is getting power and the first stage of the DME relay is working. If not check the ignition switch or any factory-alarm or after-market alarm unit.

And last but not least why are you starting this new thread instead of continuing the previous version here input needed for no start. Maybe more efficient to keep everything in the same.

Good luck,
Ingo
__________________
'74 Targa 3.6 (not stock ) - '01 C4 (almost stock) - '00 ML430 (stock)

I repair/rebuild Bosch CDI Boxes and Porsche Motronic DMEs
Porsche "Hammer" or Porsche PST2 - I can help!!
How about a NoBadDays DualChip for 964 or '95 993

[A horse with no name]

Hi ...I just read your post on my new thread.

I understand what who are stating in how the replay works in conjunction with the ECU aka DME. Thanks for the info. For clarification, there is no power on #35. I should then open up the wiring harness that enters the 'box' - Correct?

Update - Correction... No power on #18 or #35 on connector pins.

[A horse with no name]

No, there is no 'click' at the relay when I turn the key on. I have the covers off both of the DME's, and the points do not move. I also took the ICV off and cleaned it with carb cleaner. It did rattle when I shook it before I did so. It appears though to rattle a little easier now. I assume that there is no vibration due to having no power.

BTW, the alarm was disconnected many years ago and the ignition switch is about two years old. There are no other aftermarket items running off of the ignition switch. I do have an aftermarket amp which runs through original the radio head. I use my iphone for my tunes and it is plugged directly into the amp. I do have a separate on-off switch for the amp which is for the iPhone.

Again, any thoughts on why the DME relay won't work when jumped?

In the morning I'll open up the harness to the ECU to see if a wire is broken or whatever.
__________________

[ischmitz]

OK, if the DME relay stage 1 doesn't switch when you turn the ignition to ON check if you see power at pin 86 in the DME socket. Measure against pin 85 (GND) in the socket and against a metal surface. If the later works you are missing ground. If neither works your issue is at the ignition switch or alarm module or wiring. If both work and the relay doesn't click audibly when in the socket it's bad.

Cheers,
Ingo

[A horse with no name]

I just rechecked the pins, and pin#1 has 12V+
While there, I quickly took the cover off of the connector, and all seems to be OK within it, including about 3" into the harness. I'm also going check into the wires at the DME relay.

Thanks so much Ingo!.. I'll give everything you suggested a go in the morning.

[Quicksilver]

Originally Posted by A horse with no name

. . .
I have opened up my old and new DME, and when the key is on, or when trying to start it, the points in both of them do not activate. The one thing that is baffling me is that when I jump pins #30 - #87 -#87b, the pump still will not engage.

#30 has 12V. I have done and redone many electrical checks. What am I missing???...
. . .

As a first detail: It is important to be precise when discussing a technical subject. If you create confusion by using incorrect terminology you will get incorrect imprecise responses.
Above you say "DME". I can infer that you actually mean "DME Relay". There is a huge difference. DME is "Digital Motor Electronics", ie the computer and it is expensive and complicated. "DME Relay" is a switch that turns on the fuel and part of the DME. It is inexpensive and rather simple.
Be precise. [disengage pulpit]

-----------------------------
Back to the task at hand.
The issue you mention above needs to be resolved before you go any farther. If jumping the DME relay doesn't fire up the fuel pump it is an obvious failure and you can't test anything else until it is resolved. You must be able to turn on the fuel from that connector otherwise you will never get it to run.

You need to trace the wire back to the fuel pump.
- I would first check and see it you have continuity to the fuse block. The least likely of failure is the wiring harness from the DME relay to the fuse block so let's rule it out first.
- Also check the continuity from the DME relay plug to ground. If that has continuity then the harness is shorted and is a serious hazard. (Very unlikely but you are there so check it.)
- Check the fuse block, it's connections, and the fuses are a common failure. Check where the wires terminate, the screws, and the holes where the fuses rest in the blades. They must be clean to carry current and of course they need to have continuity.
- Check the wiring from the fuse block to the fuel pump. (Actually you have already done this when you jumped the fuel pump but if someone reads this it should be complete...)

Weird question: When you jumped the DME relay connector did you connect to the mirror of the diagram on the bottom of the relay? (It would be a normal type of mistake...)

------------------

Originally Posted by A horse with no name

. . .

I replaced the new DMT with the old one. When I turned the ignition on I could hear the fuel pump with both of them. Can't say that I noticed that before. After checking things out for sometime, the pump now doesn't go on when I turn the ignition on. I did jump the fuse for the pump -#6 - and it works. I kept it jumped for a moment while I cracked the rear fuel rack plug. It had pressure.

. . .

The fuel pump is not supposed to turn on when you turn the key. If the fuel pump comes on by just turning the key to the run position then something is wrong. (You could conceivably get a car to run this way but it would still be wrong.)
The DME relay is there so the DME can control the fuel pump. If the DME isn't running the motor the fuel should be off.

[A horse with no name]

OK... I still have no power on the DME relay pin #86.

I took the heater, etc out to recheck the alarm module. It's harness connector was unplugged and of both the plug(s) and the module were taped over and secure.

I have removed the back of the ignition, and all of the main -red- wires have 13 V.

With the cover off of the DME female relay, all of the wires were in excellent shape. Again, power only on pin #30. I did ground #85 as suggested, but it appears that the ground is OK as it didn't change the no power on relay pin #86.

I removed all of the top and bottom screws on the fuse bar and cleaned them up with some sand paper. I did the same to the three fuses in the engine compartment.

I peeled back the wiring harness on both the DME relay and the ECU/DME, and they also are 'as new'.

What is there to try next, or is there?

[A horse with no name]

Being that the ignition switch is only two years old, it turns the starter, including things activates the fans, radio, electric windows etc -all work...I consider it not to be the problem.

The coil checks out, as do both the speed and reference sensors. The issue seems to be that of not having any power other than #30 on the relay, including the fuel pump does not work on a jump of #30 & #87b.

It appears that I better get BCAA in here to tow it to a shop.

[rick-l]

Slow Down!

There are so many conflicting (improbable) test results my head is spinning.

Main one ---- fuel pump runs when you push down the wiper but not when you jumper the DME relay and no power when you jumper the DME relay.

[A horse with no name]

Correct...The car ran well and it is in v good condition throughout. It has always been garaged, and is only licensed from May 1st - Nov. 1st. What I am saying is that there is no corrosion anywhere on the car. The electrical harnesses are all in excellent condition,

Whatever has happened, happened after I changed all of the sensors, DME relay, and a SW chip. I can read schismatics and have rebuilt engines...This issue has truly got me baffled big time. Thanks for your interest.

[ischmitz]

Fully agree. You need to solve one issue at a time. First, you need to understand why the 1st stage of the DME relay doesn't turn on. I had posted a simple set of tests where you check for power from the ignition switch. Without that nothing else matters. Don't open harness to the DME as that is downstream from your issue

[A horse with no name]

I must find out why there is no power at pin #86. I know that it is the key to opening up the other side of the relay, fuel injection etc.

Being that it is switched, would you happen to know what the pin # on the ignition switch is? I know from having the relay apart, that it should be one of the four red wires on the ign. switch.

Thanks for your patience in advance

[ischmitz]

The alarm module usually INTERRUPTS the wire from the ignition to the relay's stage 1. Unless you have a jumper installed a car without alarm module will not start. Just saying....

[Lake Guy]

Wow so my post on the other thread (regarding this issue) may have been a bit premature. Looks like lots of awesome interest and support on this thread. Keep digging Horse you'll figure it out.

[A horse with no name]

Unfortunately I still have no power on pin #86 on the relay. From what I understand is that pin #86 on the relay is controlled by the alarm unit which is output pin 87a.

Just making an edit.. re 87b being part of the alarm. I have read that it is the black wire that connects directly to bus 15 at the unfused side of the turn signal/back up light fuse. In the 'Run' position it has 12 V.

Now 'IF' the relay has a malfunctioning factory alarm, how do I check to see if is 'malfunctioning?

There is still no power on fuse #7 but there is 12 V on #8...I understand that these two are the 'Run + Start' positions which is also #15 on the ignition switch...Is this correct?


What is new, is that by jumping #30 and #86 it will power the fuel pump. #86 is a thicker red wire with a greenie-gold stripe. On the fuse block it is #7. I ran a continuity test on it and it is OK.

Question: How can I check if the fault is in the ignition switch? I said that it was two years old but I see that it is now four years old, but with very few starts, relative to a daily driver.

The switch or the alarm seems to be the only things that I can narrow it down to.


Input please...Thanks

[A horse with no name]

Originally Posted by ischmitz

The alarm module usually INTERRUPTS the wire from the ignition to the relay's stage 1. Unless you have a jumper installed a car without alarm module will not start. Just saying....

I pulled the heater etc., out of the way to get at the alarm module again. The main plug, consisting of four separate pins, is disconnected but the two pin, 2 wires, are still plugged in. They are the horn wires. One red and the other is red/white.They are still hooked up on the bus block...I tried starting it with them unplugged but it never made a difference.