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Lol desperate times right? Looks like I get to go cigar shopping. That might explain the MPG readings I was getting while driving the car. I think you’re right though. The car has run perfectly and driven smoothly after putting the intake back on and changing the AOS seals and such but I tried something I figured I’d run it by!
Unfortunately I haven’t had word back from the guy who was willing to loan me an ECU. First things first though I’ll spend some time really correcting any possible leaks and see if I can figure out a way to add a regulator to this rigged system I’ve got and see if that helps trace the leak. I agree with you I don’t think it will solve my no start, but maybe that’s whats killing my plugs.
Say... hollween is around the corner, I’m spitballing here but would it be dangerous to try and use one of those fog machines to find a leak?
Dangerous? Doubt it. Effective? I don't think they push smoke with enough pressure? How would you connect one?
With the smoke I’m not concerned about pressure. I’d want it to do its thing and flow and see if it seeps out from anywhere.
To connect it im thinking take out the air box and AFM and use like that AC plumbing stuff and screw one end over the fog machine and use a 2 inch peace of PVC or something as a fitting to seal the JBoot on to. I just was a little sketched out by the fog solution leaving deposits or drying out seals stuff like that.
With all that trouble, buy pvc end cap 2 piece, make the adapter, and do it the right way, perhaps using your compressor and a cheap **** psi control. This is the adapter I made... easy peasy
This thread summarizes the diagnostics used to solve the mystery of the random engine no start.
My latest tests and analyses led to: the DME harness is OK; reference and speed sensors are OK; coolant temperature sensor is OK; AFM was rebuilt and OK but probably did not need to be rebuilt; TPS is OK; DME relay is OK; fuel rail pressure is in spec; 3 of 4 fuel injectors were bad by testing (removed the fuel rail with injectors from intake manifold and placed each in a cup and observed quantity of fuel in each cup after cranking engine x seconds); switch the good injector with a bad injector in each bad injector position and the good injector fired in all 4 positions(verified the fuel injector harness is OK; removed distributor cap and verified no playing in rotor with camshaft and cheese head screw was tight, rotor OK, and distributor cap OK; remove one spark plug and placed the plug attached to spark plug wire, cranked engine and there was spark (BUT this does not verify the spark plug is firing when installed because the cylinder compression pressure lowers the resistance between the electrode and ground between especially if the plug is fouled with carbon deposit on the entire porcelain insulator or a crack in the insulator(there is an internal short and no spark);there was tech bounce when cranking the engine (good reference and speed sensors);
All of these tests except the fuel ingector flow rate test indicate OK and good ECU.
Sent the injectors for cleaning and testing. Reinstalled the cleaned injectors and the engine started and then it did not start. On these no starts, there was no indication by change in noise that the engine was trying to fire, ie combustion but no run as previously before the injectors were cleaned.
Removed all spark plugs. There was uniform carbon deposit on the porcelain insulator for the entire length encapsulating the electrode of each spark plug. My assumption is in place in the cylinder head, the carbon deposit tracked the spark to ground and thus no spark for combustion. And yet, the removed spark plug produced spark when grounded to the intake manifold.
Replaced spark plugs and the engine started. Repeated the restart twice within 30 minutes and the engine fired and ran.
Tomorrow, retest to see if engine starts. If it does, then the mystery is solved.
The bottom line is complete all if the tests in Clark's Garage.
The data collected is the pieces of the puzzle and sets what is next piece to insert, do not be a parts changer, expensive and frustration.
If you added fuel injector cleaner to the fuel tank, which I did a couple of times, is not a good thing. The cleaner cleans the supply line after the filter and deposits varnish deposits in the fuel injectors. Probably an outcome that caused my injectors to foul, clogg, leak, dribble, and not pulse.
IMO, the tortoise wins the endurance race every time, patience, test, analyze the test data finds the "brass ring."
I thought I had it 2 days ago but ignored the carbon deposit on the spark plug electrode insulator as a non-issue. Tomorrow's cranking the engine and if it fires, then the problem is solved.
Post the outcome on 10/19
Last edited by T&T Racing; 10-19-2018 at 07:12 AM.
Well another piece of the mystery solved yet somehow no closer to solving it lol.
Finally knocked out the injectors and had fhem tested. 3/4 were bad and were replaced. All were cleaned ultrasonically and flow tested. Here are the results both pre and post test.
unfortunately the car is still showing the same symptoms. Car runs rough unless I disconnect the AFM. Car won’t start unless I pull the fuel pump fuse. Zero clue where to go from here. Any insight guys?
Did you ever check the temp sensor in the AFM, and the pathways between it and the DME? Did you ever find out where your fuel pump was getting power from if the fuse was removed?
If either of these was addressed I apologize. I'm not sure I read EVERY response thoroughly.
Did you ever check the temp sensor in the AFM, and the pathways between it and the DME? Did you ever find out where your fuel pump was getting power from if the fuse was removed?
If either of these was addressed I apologize. I'm not sure I read EVERY response thoroughly.
I tested the wiring harnesses for all of the sensors looking for shorts and couldn’t find any but that’s about all.
The temp sensor is a brand new unit
the AFM is a tested good one.
The fuel pump is not getting power when the fuse is removed so it’s not running which is why this is so weird. It doesn’t get any voltage and it is not pumping. For whatever reason the car refuses to start unless I kill the pump. Everything in the entire fuel system has now been replaced save for the lines and the Damper.
This is quite a lengthy thread I’m debating starting a new one.
I read a good portion of this thread but admittedly skimmed over some of the later threads. Being an original L-Jet guy on 914’s, I have to ask if you e checked or replaced the ignition switch. The early 944’s had the same type switch as the ‘75/‘76 914’s. In the 914 a failure of the switch causes a no start issue. What happens with the switch is that the plastic housing cracks from heat, causing start/no start situations.
id have to look more at an early 944 schematic but I’d guess the switches are similar enough to be causing a start/no start situation. I don’t know that it would be causing the fuel pump running without the fuse in thing because I’m not sure how the fuel pump is energized on later L-Jet/Motronic vehicles
Okay I have no idea how to describe this other than for whatever reason this relay suddenly opened and closed very rapidly for no apparent reason. I shut the car down and tried to restart but nothing until I pulled the fuse. The relay did not replicate what it did again.
To answer the latest question yes the ignition switch was checked out by the first shop I took the car too. You’re exactly right in that heat causes them to crack and can cause a no start. Unfortunately this isn’t my issue.
Car is still smoking pretty bad and smells horribly like gas even though I changed the oil again. Still looks clean too.
Say would it be possible to just swap out every single part of the wiring harness in the car one at a time? Something along the lines of Lindseys offerings for the injectors and speed sensors but for the entire car? Can’t imagine it would be cheap but I mean, what the heck else can be causing these issues?
Ill start another thread to eliminate all the what if’s and save everyone some time. I’ll come back here and post a link.
Jacob, sorry if this has been covered already, but may I ask how did you hook up the fuel pressure gauge?
Did you run a line from the rail into the car? If so, through where?
I opted for a digital gauge so that I wouldn’t be running a line of gas into the car. I’ve actually been meaning to make a video on this for my channel so I’ll keep this reply as short as possible,
the sending unit for the gauge is tapped tapped into the end of a spare fuel rail cap. No leaks nice and tight. The wire for the fuel rail pressure sending unit then follows the wiring harness for the injectors and the rest of the wiring harness back along the firewall and follows the stock harness for the windshield wiper motor. From there I just fed the wire behind the dash to where th gauge is. It’s currently sitting where the clock used to be next to the oil pressure gauge. Lighting all runs from the dash light circuit so it comes on with my headlight switch. It gets power from the radio so it’s swtiched 12v with ignition
I opted for a digital gauge so that I wouldn’t be running a line of gas into the car. I’ve actually been meaning to make a video on this for my channel so I’ll keep this reply as short as possible,
the sending unit for the gauge is tapped tapped into the end of a spare fuel rail cap. No leaks nice and tight. The wire for the fuel rail pressure sending unit then follows the wiring harness for the injectors and the rest of the wiring harness back along the firewall and follows the stock harness for the windshield wiper motor. From there I just fed the wire behind the dash to where th gauge is. It’s currently sitting where the clock used to be next to the oil pressure gauge. Lighting all runs from the dash light circuit so it comes on with my headlight switch. It gets power from the radio so it’s swtiched 12v with ignition
Thanks for the info! Look forward to that Youtube video
10-17-2018, 07:53 AM
