85(early) 944 starting issues...

[Outback Porsche]

DME from an 86 won't work unless you change the AFM also.

For 944online, I think the details are on their web site.

If your game, you could open your DME and look for bad solder joints. They are not always obvious though.

Personally, I don't yet trust your relay. I think the replacement you used is dead. I'd borrow your mates relay first before swapping out his DME and AFM.

Cheers,

[shiftdrift944]

ok ill check out 944online, yea i think both or my relay r bad cause i check volts from the fuel pump and crank the car n no volt were registering to the voltmeter.

ill see if i can try to rebuild the dme i have just to see if i can revive them...

[HondaDustR]

Originally Posted by shiftdrift944

well couldnt i just re heat the solder joints? if i could do it, but does anyone have any hits or tip so i dont end up messing the dme?

Use a small ~30W pencil iron and heat only enough to re-melt the solder joint. If you do need more solder, use only rosin core solder and use the thin guage so you don't make a mess. Just get the joint to melting point and feed a little bit in, making sure not to use too much and make the joint all blobby, and definitely do not allow solder to flow and bridge two adjacent connections. Make the joint melt the new solder, not the iron, when adding more or you will get a poor quality joint. Most of the time, just re-melting what's there is enough. Pretty easy, really. Just don't overheat anything by leaving heat applied longer than needed and don't bridge connections. You can get the iron and solder at Radio shack or a good hardware store.

[shiftdrift944]

ok thanks honda. yea i have a pencil iron i can use, ill see what i can do on the dme. i resolder and added solder to the points on the dme relays.

[shiftdrift944]

ok could all of this be cause by a bad o2 sensor aswell??? i read somewhere in a forum that the wire from the 02 sensor and the dme relay are connect some how? im no sure

[Outback Porsche]

Californian cars have an O2 sensor with a heater element inside it. The power for the heater is on the same circuit as the 12V for the DME (via the DME/Fuel Pump relay). Would the O2 sensor cause this fault. Is the car from Cal?

Idle/CO level is on the list below and falls under both symptoms of 'Poor Idle' and 'Poor Pickup'. If the bypass port on the AFM is blocked or the screw has been set incorrectly, the O2 sensor may not be able to provide adequate feedback to the DME to fine adjust the fuel map. And if you have a combination of both a poorly set AFM bypass and a bad O2 sensor, you would probably have this exact problem.

Something else to check, I suppose? If you fiddle with the AFM bypass, you need to get hold of a gas analyser to set the CO level correctly (procedure is in Workshop Manual Vol1).

You may have just nailed it.

Here's the DME troubleshooting list from Vol1;


combining 'Poor Idle' and 'Poor Pickup' columns gives you a few choices and eliminates a few. Most likely cause of fault is the lowest row number.

Cheers,

[shiftdrift944]

yea the car is from cal.

[Outback Porsche]

Thought of another possibility re O2 sensor. If the heater element went bad so that it was loading down the 12V to less than 8V, the DME will no longer operate.

That should be easy enough to check for at the dme plug when you attempt to start the car.

Cheers,

[Outback Porsche]

or you could just disconnect the O2 sensor and see what happens.

[Outback Porsche]

Originally Posted by Outback Porsche

symptoms of 'Poor Idle' and 'Poor Pickup'

lol, sorry it's late over here and I got confused between your issue and another one I've been monitoring. Hope I didn't confuse you too much.

I should go and get some sleep

Cheers,

[shiftdrift944]

its ok outback, i think i got the o2 sensor from one of your post i read(maybe the other one ur monitoring).

but switch pin #'s should i check for the o2 sensor or the dme wiring when i go to start the car?? cause i have the dme out and can possibly check the wiring tomorrow if it doesnt keep snowing...

i have a print out of the dme pin and what they do but im not sure witch one's are from the relay and the following link: DME Connector 35-pin

i also have a newer AFM(2) i not sure of the part number but it has the black wire on top and mine didn't before. i replace thinking it was the AFM(1) that was bad, but i see now that their is difference in volt from the 82-85 from 8V to 12V compare to the 85.5+ is only limited to 5 V. could this also be another reason? cause i can switch the chip cause stupid me messed with the spring inside(this is before i knew i shouldn't mess with the spring) and i think it wouldn't work if i just swap them. ill have to check volt from the AFM by testing them both the stock and replaced one. I found this that helped me: http://e28-535i.com/technical/AFM%20Repair.pdf
THe one installed right now.


and yea ill disconnect the 02 sensor and see if it works if not then the AFM is the one that messing things up this whole time...

[Outback Porsche]

That's a late model AFM pictured - you can tell by the style of the ceramic pcb. It's not going to work with your early DME.

If you go back to your original AFM, the car should start. It may run rough but considering everything else done (sensors etc), it should at least start. It's a bugger that you had a play with the spring . It may be time to jump on evilb*y and find a good early AFM.

At least your friends 86 DME should also start the car with this later AFM.

All the schematic info you need (and more) is here Manuals

Cheers,

[shiftdrift944]

yea well i had the late model one this whole time and i got it to start for several time but then later it wouldnt start... so i dont know that was possible...??? either way ill see what i can do with the afm i think i put marking on the gear but im not sure if i but it back to where it should be... but cant i just change the pcb?? or would the spring not be compatible with the early pcb??

[shiftdrift944]

so i dont know how that was possible?? ***

[Outback Porsche]

Is the DME an early or late? What are the numbers on it?

[shiftdrift944]

its a early one, the part number is 944.618.111.01

[Outback Porsche]

Well, bugger me! It's not supposed to work? Hmmmmmm!

Did it run like crap when it did start?

In the early AFM's the resistors are set up so that the voltage output is an exponential relationship to the opening of the barn door. In the new AFM it's a linear relationship. The fuel/timing lookup in the DME should be all wrong?

I wouldn't advise swapping parts in and out between the AFM's. I would suspect that they are designed very specific to each model.

Test the ignition system using your friends DME, if it works you know what the fault is. If it doesn't, the go down the path of the O2 sensor (or do the O2 thing first - it doesn't really matter).

Ultimately though, your half way towards an upgraded engine control system. I'd find myself a newer DME anyway.

If you do the later DME you'll need to get the later AAV or cold starts will be a problem.

Cheers,

[shiftdrift944]

hahaha no it started and it idle good!! but this only worked for like 2 or 3 times....
ok so before i played with the early AFM i marked it and i had just incase i want it back, so i align it so it should be good.
ill see if my friend want to swap it out but hes only consern it will mess his up?

but either way i disconnected the o2 sensor and had a voltmeter connected to it (c2 plug on rear of engine) and i had to put a battery started but the volt would go low as 10 and rarely hit the 12 constanly? is it good the volts go down? my guess no...

and it keep doing the same thing it about to start but then it dies and i check the volt going to the 02 plug and it was 10 or so...so the fuel pump isnt getting direct 12 and i jumped the DME/fuel relay with all the test above.

[shiftdrift944]

oh and i just swapped the AFM but i didnt had it all hook up to the air box but it wouldnt start either, but it did seem like it going to start (its easier) but i think the fuel isnt getting enough pressure for the injector to fire.