Hello everybody,

My 1994 sl500 wont crank (wont spin over) and the fuel pump does not work. Last week it cranked fine and fuel pump worked, sat for a week..now nothing. I have xentry and ran the codes, will upload the pictures.

First just to get this out of the way;

-fuel pump relay works, tested that
- first problem was transmission neutral saftey switch. Bought a new one, that works now but still no crank
-throttle body clicks and does its thing when i turn the car on

Here are all the codes i got:

 

Disclaimer: This car has the v12 swapped in and has been wired with all stock computers and harnesses etc..


Now for the weird part....

I know the seat belt switches wont have anything to do with the car starting but the fuel safety shut off switch...would that cause it? I have looked up and down this forum and google and cannot find anywhere where this switch is located.. When i manually go into each control module from xentry, It can still communicate with N1-N4 modules. The 10amp fuses in the GM module are not blown and i just changed them to make sure. When i read "actual Values" i get all components working and all of them have check marks highlighted....

Also the EZ computers cannot communicate with xentry, but this was happening when it was able to crank over...

The big thing here is if anybody can shed some light if any of those codes would prevent the car from starting and also at the same time prevent the fuel pump from turning on.

 

If anybody would like to offer help i can upload more pictures with regard to what i am talking about in case there is any confusion. My hunch is the reason the fuel pump isnt working is due to that safety switch, but as for the engine not turning over im kind of at a loss since literally just 7 days ago it cranked fine without a problem and at first i thought it was neutral safety switch, which was bad, but after changing that still nothing..
battery is also brand new and 1050 cca

 

After doing more research on all these codes combined, is the reason this car not starting due to a safety feature? All the codes that are shown would be caused from an accident (if this car was in one) so would a new airbag control module fix this issue? Also I cannot find any info about a separate fuel safety cutoff switch or inertia switch..The only thing I can find that closely matches my search points is a inertia switch made by SMP Part Number: 90mer300sl/FV-7 but one look at the switch itself and it definitely does not fit my car..

does ANYBODY have any information about this?...I guess i will need to take it to a dealer as i imagine this is one of those issues that happens to nobody and if it does thats because you got in a wreck, but you total the car so none of the airbag codes and safety switches get replaced or diagnosed..My luck..

 

Have you tried clearing the codes, try to start the car and then read codes again? It's possible a fuel cutoff switch could also tell the computer to not crank. Have you looked around in the trunk on the right side? I'm not sure where else on these cars the switch might be. In a lot of cars its in the trunk, glove box or under footwell panel in the driver or passenger side.

 

So i spoke with victor at restoreyourmercedes.com and he gave some pointers.

-battery is 2 weeks old, checked voltage, 12.5v.. its not battery, also did the dreaded thing of jumping the car. Did it with my diesel truck with 950CCA still nothing
-stuck a screw driver right at the starter to bypass the bendix and see if the motor would at least spin, had a very weak spark when i did this and nothing happened (ill explain more on this below)
- decided to jump starter directly with a battery, spun great..so its not the starter (Maybe bendix??..highly unlikely..will explain below)
-replaced K38 relay, nothing..decided to bypass relay and connect both violet/with green stripe wires together (per victors suggestion) and still NOTHING
-according to victor for my car that fuel safety shutoff is not a switch and does not affect the car from turning on. it is something that is within the throttle bodies, if they get stuck not in sync or whatever it will throw that code and that just limits the fuel injector output. (victors understanding..would have never guessed this). Maybe there is a short in the throttle bodies preventing it from starting...

Now for more in depth analysis:
-When i jumped the starter directly with screw driver, a click noise comes from the top of the engine (no, not the starter, had my hand on it..did not more/vibrate or do anything). Upon further investigation its the fuel injectors that are clicking. Since i did not turn the key on the ignition, but rather jumped the starter directly with the screw driver..i have no idea why the fuel injectors would click or basically activate..might suggest a short in the computer/fuel injectors somewhere when you give it power but i have no idea how to test this..maybe i am wrong and this is normal
-possibly alternator has an issue of some sort (alternator is new, my opinion highly unlikely) because the main starter wire also directly connects to alternator. After the car cranked fine i went ahead and installed this new alternator. After i installed this, i did not try to re-crank the car. it then sat for a week so this MAY be the problem..but i highly doubt it. I will disconnect the alternator sometime today and update later. Also the battery has not gone dead from sitting so there is no sign of a short
- keep in mind the car literally cranked fine, sat for a week and now its not doing anything so i did not make a mistake when i initially put all the v12 components, body harness and engine into the car and im not a believer that this would magically just break from sitting for a week (i could be wrong, but i need opinions..totally lost at this point)
-fuel pump now works, replaced the relay in the trunk and that fixed it..although the fuel pump sounds a little rough now


Still following?? lol

So i think what the problem is, is the starter is not getting enough power and something along the way in the computer or wherever is shorting out when i give the car power. this in turn drags power away from the starter and it does not have enough juice to spin. At this point i am only guessing and the reason i have came to this conclusion is because when i jump the starter with a screw driver, a very weak spark forms..sometimes its barely a spark at all. Only problem is, as i have mentioned, the car cranked fine a week ago..how would this happen if i did not touch a thing?/ Where would i look??

In summary:
- weak spark when trying to jump starter, i will get voltage at starter later today as well
-fuel injectors click when i jump starter with a screw driver. This may be normal but my common sense says "no" because i did not turn the key, car is off. Possible short which may lead to the issue

SOS

 

Checked volts. When ignition is off, 12.58 volts, ignition on, it drops to near 0 (0.07-8). Disconnected alternator, no change

Any suggestions on where to check? Anybody had this issue before??

 

Immobilizer??

 

What is the month and year that your car was manufactured? In late '94 the K38 immobilizer relay was eliminated.

By the way, the fuel pump will not run if the engine is not turning.

 

According to a vin decoder 12/20/1993

Vin WDBFA67E9RF097042

 

Check fuse #8 in the main box in the engine compartment. It supplies power to the coil of the K38 immobiliser relay.

 

Fuse is good, dont see where it says anything about a starter relay

 

The chart mentions nothing about your transmission kickdown solenoid, but you know it exists.

One side of K38's coil goes to the fuse; the other side gets grounded through the alarm module. I'd try bypassing the alarm module. To do that remove its electrical connector and use a paperclip or wire to jumper together connector sockets #4 and #5. With the key on, K38 should definitely be energized.

The alarm module is mounted to a metal plate located above the battery and is mostly hidden. I think the sockets are numbered on the connector.

 

Alright so here is the update. I re-wired the k38 back again (previously had it bypassed), went into xentry and i could manually turn the solenoid on and off and i could hear it audibly make a clicking noise. While it was manually turned on, tried to crank the car but got nothing. I checked the volts at the starter while the relay was on and it was fluctuating at first bouncing between 3 and 7 volts, then stopped around 9.5 volts. (checked battery and still had 12.2 volts) I didnt jump sockets 4 and 5 mainly because i dont have a paperclip or wire laying around that is small enough to fit. I unplugged both of the modules in the trunk you mentioned just to rule that out, car still did nothing, checked the trunk fuses and i changed them all out. (sl600 donner car managed to pull off the fuses and relays..but i did not take any of the alarm modules..)

Did some more digging and i turned the key as if to start the car normally and i could not feel or hear the relay make a clicking noise anymore, its not energized at this point. I would think maybe the alarm modules are bad but i could communicate through xentry with them and i could do all the "actuations" and read the real values etc.. Also the relay was fairly warm to the touch

When the key is completely off, starter has 12.2 volts, key on, 10~ volts. When i had the k38 relay manually turned on, volts at first jumped around but then stayed around 9.5 volts as previously mentioned.

Maybe this could possibly lead to bad alarm modules??? Also looked for codes and xentry showed none

Also when i turn the key the ignition switch still turns all the dash lights on, The switches on the center console all blink once, throttle bodies click, abs pump hums and the car does its thing normally so i wouldnt think its the ignition switch unless the starter function of it is separate from all the rest.

Summary:
-manually turn on and off k38 relay through xentry, you can hear it click
-tried to start the car normally, k38 relay is no longer clicking, or showing any signs of life
-key off, 12.2 volts at starter, key on (but not in the "cranking" position) 10~
-when k38 was energized manually through xentry, starter volts where fluctuating 3-7 volts then stayed around 9.5
-k38 relay fairly warm to the touch (i would guess about like a hot shower, maybe 102-3 degrees F..guessing though)
-no codes present on the modules through xentry, communicated fine and could read all "real values" as well as actuation's

 

By "ignition on", Kyle, you do mean to "position 2", right? (Position 3 engages the starter.)

 

Sorry, should have been more clear in that post. I was referring to position 3 (actually cranking the car)

 

If the voltage on the battery drops below one volt when you try to start the car, then the battery has to be bad. There is no other possibility, But before having it tested or replaced, be certain that your meter is making good contact with the battery terminals. (Since the battery is just a couple weeks old, there shouldn't be any corrosion on the terminals for this to be an issue.)

 

Ok ill check that, but when i turn the key to position 3, i dont hear or feel the k38 solenoid click. Is that a problem?

 

Just checked battery and it does not even flinch when i try to crank the car. Checked k38 again and it does engage..

So at this point am i just screwed?

K38 works when i turn the key and car battery is at 12.3 and doesnt flinch when i turn the key to position 3.

Anything else i could check?

 

You aren't screwed, Kyle. Troubleshooting this problem is straightforward and nearly always leads to a resolution. But it can be a bit tedious.

I presume you do not hear a "click" from the starter solenoid engaging. If so, then you just follow the voltage from the battery to the solenoid while the key is in position 3. The path is battery -> ignition switch -> K38 socket #3 (terminal 30) -> neutral-safety switch -> solenoid. I note that its best to measure voltage without removing a component from the circuit, since the open-circuit and closed-circuit voltages will be different in the case where a poor contact has significant resistance instead of zero resistance.

If you haven't got an assistant to turn the key to position 3 while you take measurements, then you might try putting the key in a vice grip and then suspend a weight from the end of the vice grip which applies torque to the key and keeps it in position 3. (Years ago I had to tap my starter with a pool cue, and I used the vice grip method to hold the key.)

By the way, is K38 in the main fuse box?

 

The k38 is right next to the steering colum under the dash. Well considering the fact that the battery is good, k38 is good, ignition switch is good, starter i presume is good ( brand new) then the problem may be between neutral safety switch> starter. I dont know if i mentioned this in my original post but the very first thing i checked when this car would not crank was the neutral safety switch. Checked xentry and it was bad, displaying the -F-. So i changed that and now i can see the real values in xentry, but what sockets would i check and what would i look for? Low voltage or drop in voltage or resistance? Also is there anything connected to the transmission that if bad, would prevent the car from cranking? Besides the actual neutral safety switch

Side note, how would I check the starter bendix? That would be the only other thing i can think of that would prevent the starter from working. I do not hear the starter clicking, but to my understanding the starter bendix engages the gear as well as alows the current to go through to the starter?

 

Just to clarify this; "but to my understanding the starter bendix engages the gear as well as alows the current to go through to the starter?"

Im talking about the motor.

I understand the motor and bendix make up the starter

 

If you were to purchase a starter motor, it would include the solenoid. So I think "starter" refers to the motor, bendix, and the solenoid.

There isn't a formal test of the bendix, per se. If the starter is engaged and: (1) the spinning starter spins the engine, and (2) when the engine starts the starter disengages from the flywheel, then you conclude the bendix is working fine. Failure to meet either of the two criteria indicates a faulty bendix.

 

So everything works..how can i bypass the neutral safety switch?

 

Do you know how to bypass the neutral safety switch? Im at my wits end with this car.. the first and technically only problem i found was the neutral safety switch so at this point that has to be the problem..