Another no start issue

[Emnyama944]

Hi All,

I've been struggling with a no-start issue on my 951 for a little while now, I've done a lot of research and it seems there are some very common issues and no matter how deep we dig it always seems to come back to one or two things so I'm sure I have nothing new and I'd appreciate an expert or even a novice telling me what I've missed.

The issue I'm seeing is that the car starts and runs for a few seconds before it dies, if I hold the key in the start position or jump the DME relay the car runs. I've changed the DME relay and I get the same issue.
I think I've narrowed it down to the speed and reference sensors, when checking the sensors I'm getting up to 8 volts on the speed sensor when the car is starting but I'm only seeing 0.4 volts on the reference sensor, according to all the documentation I've read I should be seeing 2 volts on the reference sensor, I've bought 2 new sensors and they both give the same results, I'm checking the voltage right off the reference sensor and it shows 0.4 volts.
I'm assuming there is an issue with the distance between the reference sensor and the flywheel but since the speed sensor is set correctly I'm at a loss for how this could be the case.

Any questions or assistance would be much appreciated.

Thanks,
Rudi

[kdjones2000]

May be your ignition switch...

Also, make sure that your AFM connection is plugged in - if not it will start then die.

[chip18]

Well it's early in the week and most likely a slow day, so I'll take a stab. And in as much as my 89 951 has now decided to pull the "No Start" crap, I fell your pain! But hey it's better than the "won't go into gear while running bit??? "Yes, that was fun!!!

And the "issue" was none of the usual suspects??? I solved that one thru sheer "Dumb Luck!" Sometimes it's better to be luck than good.

But back on point ... depending on "who you believe??" Checking the sensors resistance and voltage, is not that useful??? "They say the best way to check those sensors is with the use of an "Oscilloscope." With a scope you can "see" the square wave and that tells you if the sensors readings are good. Since I have already DVOM'd, them and my specs were in range?? I tend to thing that "they are correct." Cuz mine "spec'd" fine and my car still won't start!!

But short of a scope there is a new tool out there for our cars for help in diagnosing this issue. : https://www.youtube.com/watch?v=2SJCwJo8QPs

It seems pretty cool! I've not got one myself Cuz well, I'm pig headed and stubborn!!

So back to basics. If your car will start and then dies?? That strikes me as a bit different?? Mine did not start and I had no fuel pressure at first?? And I swear at some point I had swapped the DME and jumped the pins and still had no fuel pressure// And then as of a couple of weeks ago .... I did it again and had 45 to 50 psi at the rail! (It's not stock and that is what it ran great at, when it ran.)

Well that's great time to fire it up and now ... "Fuel and No Spark," WTH???" So that is where I am at currently. But your sounds a little different??

If "yours" want's to start and then dies?? Check for "spark" after it dies! I'm not sure what that would mean .. but it would mean something?? And it sounds like you do have "new" speed and reference sensors?? But what about the harness from DME/KLR going to them??? Was that replaced or are they still the OEM from what 25 years ago or so??? Those just might be your problem???

And of course .. mine have been replaced when I got it (the harness and the sensors) and it still won't start! But hey maybe the harness replacement for the sensors will work for your works?

But still before replacing anything ... you could try and jump the KLR! You can bypass the KLR it sends the signal for "spark" to the DME, bypass it by jumping pin's 9 and 16. I'd not drive it like that ... but it should continue to idle and not die if a bad KLR is killing the spark.

I have not tried on mine yet, cuz I got ticked off, again and had to walk away. But hey maybe your luck will be better.

[DannoXYZ]

Originally Posted by Emnyama944

The issue I'm seeing is that the car starts and runs for a few seconds before it dies, if I hold the key in the start position or jump the DME relay the car runs.

This is critical clue. If it starts at all, speed/ref sensors are OK. Don't waste any more time on those. Re-install original ones and return ones you bought. Fuel and ignition systems are also OK.

Measure AFM output-voltage at DME-connector when it starts. Maybe jumper DME relay/fuel-pump to keep it running long enough to measure AFM output-voltage.

What is this voltage? If DME doesn't see valid AFM voltage within 1-2 seconds of starting, it will turn off fuel-pump.

Many things can cause invalid AFM voltage:

- broken wires between AFM and DME, how can you measure and test that?
- unplugged AFM connector
- corroded and stuck AFM flapper-door, how can you measure and test that?
- vacuum-leak after AFM, J-boot can have massive tear underneath and go undetected.
- J-boot not connected to turbo
- ripped or disconnected intercooler hoses

[chip18]

Originally Posted by DannoXYZ

This is critical clue. If it starts at all, speed/ref sensors are OK. Don't waste any more time on those. Re-install original ones and return ones you bought. Fuel and ignition systems are also OK.

Measure AFM output-voltage at DME-connector when it starts. Maybe jumper DME relay/fuel-pump to keep it running long enough to measure AFM output-voltage.

What is this voltage? If DME doesn't see valid AFM voltage within 1-2 seconds of starting, it will turn off fuel-pump.

Many things can cause invalid AFM voltage:

- broken wires between AFM and DME, how can you measure and test that?
- unplugged AFM connector
- corroded and stuck AFM flapper-door, how can you measure and test that?
- vacuum-leak after AFM, J-boot can have massive tear underneath and go undetected.
- J-boot not connected to turbo
- ripped or disconnected intercooler hoses

Thanks I added this thread for future reference.

Add to add another source for a massive leak that will disable the car ... the rubber from the throttle body to the hard pipe (Inter cooler.)

Cuz, if that pops off or is not a good seal?? Hmm, the car will start ... and then die!

[Emnyama944]

Thanks That's extremely helpful, I was under the impression that the car would start and if it didn't pick up the correct voltage from the speed or reference sensor then it would cut power to the fuel pump but this makes more sense and lines up with what I'm seeing.

I had to splice in new plugs on the car side because the old wires were frayed and damaged so badly.

I have previously checked the AFM and thought the voltages were good but I'll take another look, I've also tested for leaks in the intake with an adapter I found on the internet and 3D printed so I could attach my compressor to the intake. https://www.thingiverse.com/thing:2792026

[chip18]

Well I definitely think Danno is on the right track here! But ... that throttle body hose can be a major PIA!! They are old and oil soaked and no matter how much you tighten them up, if worn?? They will pop off under boost!!

I almost got 5000 lbs of SUV in the rear the first time it happened!!! It was coming fast and kinda close and I was at a dead stop but no biggie as "I got this."

So I pull out and hammer down and you know no problem, till seconds later I heard a loud "POP??" And I got nothing ... WTH??? I drifted to the side of the road and got out of they way and headed back home and tightened it down ... again!!!

And all was well ... until the middle of the night on a 300 mile road trip to Ca!!! Sigh ... half way between where I wanted to be and home at freaking midnight!?? It happened again!! I jammed it back on and we limped to San Jose and that trip kinda sucked!! I had zero boost and a 951 with a big old low compression 4 cylinder engine with no boost ... is not a lot of fun! But we made it and when we got to my friends house (original owner) we checked it out in the day time!

And it was that hose again!! So we tightened it down again! And took it out and I hit 23 psi! Not suppose to do that with my tune on pump gas!! But a manual Boost control at 16 psi at elevation was 23 psi at sea level!

300 miles back adjusting boost down as we went (this time to keep it at 17) no issue! And it was for awhile, until it did it again!!!

That was it, I chucked the old worn out hose in the bin and bought a new one!! And added a Banjo Clamp!!! And yeah I got new problems now apparently ... But that "F'ing" hose ain't one of them.

[Emnyama944]

Sounds to me like you're having a lot of fun with your 951, lucky for me mine is stuck in my garage. I've only driven it twice, once home from the guy I bought it from and the second time to a friend's workshop where I volunteer teaching young adults automotive skills, it died on me at his workshop but then magically started again, when I got it home I decided to get to work on all the things that were wrong with it, the steering rack leaked so I pulled that and replaced the seals, while I was putting that back I noticed a bit of oil coming from the oil pump so I had to change that along with all the belts up front, I found the ground wire to the engine was corroded so I've changed that and there are still 12 dozen things that still need doing. The joys of buying a 32 year old car that was neglected.

So I found that jumping the relay means I don't need to run the car to get the voltages from the AFM, I got 5.05 volts from the input and 0.250 from the output when the car wasn't running, when I started the car I get 5.05 volts from the input and 0.8 volts at idle. I'm pretty sure that means it's not the AFM, I even checked the voltage at the DME in case there was an issue with the wires and they're the same. Do I have a DME issue or is there something else that cuts the engine after start?

[chip18]

Hmm Ok well "new" information here or "additional" perhaps?? Cuz now you mention ... no hot restart?? And then a "magical restart??" Typically that manifest itself when you drive somewhere, turn the car off and go to restart it inside of ... I don't know 20 minuets or so?? My friend had "warned me about it doing that on random occasions?? And he replaced both sensors and the harness to them before I got the car so you know ... it shouldn't be doing that anymore, but it did???

But ... unlike you, since I was aware of this possibility?? I carried with me in the glove Box a "Magic Wand!" Or you know as it more commonly called ... a "Flashlight."

So, ... after a few are you "F'ing kidding me's??!! I take the "wand" out of the glove box, pop the hood and apply the spell?? IE ... I wave the "wand" over the suspect parts, wiggle them around cuz you know ... WTH??" Climb back in hit the key and it fires up!!!??

I drive back home without incident and it never did that again, when it ran! And then came the "Hydraulic link, from hell?? Motor running and no clutch, engagement what the hell and you know of course the clutch/pp and throw out bearing had been replaced and it was all working fine???

But back on point, and yeah the fact that your will start and then did is weird-er??? And thanks for the tip for getting power to check out the AFM!

The AFM is generally a fairly simple and reliable device for the most part. I've not seen any complaints of them failing on the board.

Most owners replace them for other reason's and most of there reasons are usually "Wrong!" That reason being it limit's Hp?? Well ... not for most of us living on a budget! Slight part throttle manipulation in "The Real World Driving conditions is where you can feel the lag factor with the AFM.

Well Ok, back on point. if you take into account the prior "no hot restart issue," I think that points to a "thermal breakdown" in some component?? And I might have the same issue myself?? But if it is mine is worst cuz mine won't start at all??

But yours starts and then dies?? So simple enough ... check spark before you try and start it. If you have spark?? Try and start it. If it starts and then dies ... check spark again?? And see what you get??

As I understand ... the reason checking with a "DVOM" is insufficient, "reading between the lines" is because if the engine is cold ... it can't account for "thermal break down??" An oscilloscope let's you "see" what the Square wave, for the sensors looks like!

The first image :
Rogue Tuning - Crank Angle Sensors

The car is not gonna ... keep running! The "Carmonica" the device I linked is a work around ... it has three lights on it now. And the third light for "Power" as I understand ... won't light if there is not sufficient "voltage" to keep it lit??

So it can help eliminate issues. If the power light does not come on ... then it's most likely a KLR issue (as I understand.) Because the KLR sends the TDC reference signal to the DME!

it cost "zero dollars" to check that out! back to basics as it were.

Jump the KLR and if the car "starts and keeps running?? The KLR, is the issue! Pin's 9 and 16.



One sensor is for starting (speed ??} And the other is for TDC (Reference??) If the motor see's no TDC signal ... it won't start or you know keep running.

That's what I think is my "issue anyway" but I'm to pigged and stubborn to check it out so far!!

I finally got fuel pressure and mine still won't start!! So I'm kinda ticked off .. still! But hey that's just me ... you can't make it personnel.

[nize]

i'm surprised nobody mentioned checking the blink codes.
Blink Code Tester queston...

https://www.lindseyracing.com/LR/Parts/BLINKCODE.html

[chip18]

Originally Posted by nize

i'm surprised nobody mentioned checking the blink codes.
Blink Code Tester queston...

https://www.lindseyracing.com/LR/Parts/BLINKCODE.html

Hmm, I had forgotten about that thing! And as it happens I do have it hooked up ... and it does appear to work!? And even with my "crank and no start" ... when I tried and failed to get it started it did "Blink!!"

But as I read/interpreted how it works. You take the car for a short drive turn it off and see if you have blink codes?? Strict interpretation I suppose??? But ... if it won't start??
Then maybe it shows "why" also??? No one seems to mention using it that I know of for "no Starts"???

I'll review the info again and test it out! I'll review the blink codes again (it's been years) and test it out! But I'll film it for review, later cuz as I recall, I think it only blinks for one cycle?? By the time I noticed it, it had stopped. Thanks for the reminder!

[Emnyama944]

I just happen to have an LED from Radioshack for another project I'm working on, I tried the blink code and got nothing back. No Blinking codes.

I cant get past the fact that I only have 0.4 volts on the reference sensor but I've even checked the gaps on the reference sensor screws and made sure they are around 0.8mm from the sensor and I still get 0.4 volts and people seem to think the voltages don't matter so I guess the question is what issues causes the DME to cut power to the fuel pump or spark?

I've got all new inlet pipes, I replaced them before I started troubleshooting because the ones that came with the car were shot and my experience with old turbocharged cars taught me I don't want to mess around with old rubber pipes.

[chip18]

And that would be why "some of us hate those freaking things. The guy that made the "Carmonica" that's what he called it, is the one that said the "DVOM" was not that effective?? And I think it's safe to say that he know's what he's talking about. I have no affiliation there. And if swearing and screaming worked, mine would have started a long time ago.

But ... the fact that your Blink Code Tester, showed nothing, is kinda wired?? If the car won't start there have to be codes?? Mind did show codes with the "Blink Tester??" But as I was focusing on the coil and no start, I paid them no mind??

I'd forgotten the Blink Code Tester was still there?? And I was focused on the coil?? I just happen to look up after I told my friend stop trying to start it and saw it "Blinking??" I just thought oh ... that's weird and moved on to trying, uh something else.

But the picture on "Lindsey's" site is a bit confusing?? And since my "Blink Code" tester does work (apparently.) I'll post a picture of my setup this evening as it has no "extra" wires in there and does seem to work?? That should help, with that part anyway. As I have to get to work ...uh now!

[chip18]

OK, this is interesting?? I pretty much figured my set up was the same as the one posted?? But apparently not??





I have changed somethings on the car but that was not one of them. I did clean up the install but I did not change the pin inputs. And even though I had forgotten it was there and disregarded whatever it was "trying to tell me?? When I cranked the car it would not start ... still!! But when I shut it off, the Led was blinking!

And the info said "drive the car and shut it off," to check for codes. I saw nothing about it "blinking on "no starts??" Now if that info ... drive it and then turn if off to check for blinks, is uh wrong??? That would be pretty ... interesting??

OK, so I suppose ... now that I know what I'm gonna be looking for ... I got to try again and see what happens, with the blink codes??

[soxnail]

Sorry should have chimed in earlier, have not been on the board for a bit.
As mentioned your no start clues point to the DME not seeing a valid signal train to meet the "engine is running" criteria. It then cuts the fuel relay (DME relay) off. If you hold the key in start position then you are overriding the DME to keep the relay energized.
Question (and pardon me if I missed these in my reading of the post):

1. Did you look at pin 20 of the DME plug to see if it holds the relay on (it should stay low near zero on a Volt meter referenced to ground). If it goes to ground and then goes back up when you release the key, then the the DME is commanding off to the fuel relay. This the first test to eliminate other possibilities.
We can go on after you perform this test.
Sox
Ps. as mentioned if the car starts at all the ref and speed sensors are fine, and the DME is seeing them.

[Emnyama944]

That's an interesting bit of information, it's been a while since I checked pin 20 on the DME but I don't recall it going to ground and then back after releasing the key, if memory serves it the volts would drop to zero as soon as I release the key.

Since my last post I found a faulty spark plug wire and I notices injectors 1 and 4 were leaking, I also saw the Air Oil separator was spewing oil all over the engine, I've spent the better part of the last two days taking the exhaust apart so I can change the o-rings.

I figured while the car wont start I should take care of all the "little" issues I can see so I don't have to visit them later.

[soxnail]

The power from the key switch in start position is also routed to the DME and then out to the fuel relay. When the key is let go and the engine is at 200 plus rpm the DME takes over and holds the relay on (low on pin 20). So in the entire sequence of starting and running you should never see a high (12V) on pin 20. The only time it has a high on it is when ignition is on but not in crank and the engine is not running.
Sox

[DannoXYZ]

Blink-codes come from KLR and only alerts to boost-related issues. Nothing for speed/ref-sensor, O2-sensor AFM, ignition, zip, nothing!

Did you measure that 0.8v AFM-output at idle at the DME-connector ? Or at AFM itself? Doesn't matter one bit what AFM outputs if DME doesn't see it. With age of crispy & cracked wiring, it's not uncommon for signals to not arrive at DME correctly even if all sensors are operational.