454 Mag MPI Warm/Hot start issue

[JW in Texas]

My suspicion is prior to doing injectors, it was a combo of VL due to heat & flooding due to a leaky injector that was causing it to not start until the next day. Wet plugs wouldn't fire even with ether. Now with fresh injectors, I think it may be VL only since it started after about 4 hours, but I don't understand why if it was just a VL issue ether wouldn't help. Will you always get some kind of a pop with ether with a VL issue? Not necessarily a start, but at least a kick of some sort?

 

[alldodge]

I don't know, something is missing

 

[alldodge]

Pull some plugs and post pics

 

[JW in Texas]

Here you go, just pulled.

https://m.facebook.com/story.php?story_fbid=10216610764477940&id=1124506597

PS: Error'd when I tried to upload, thus the FB link

 

[alldodge]

There new plugs but showing signs of lean or steam cleaning from the looks of the center electrode

 

[JW in Texas]

They have about an 1 hour of time on them & got blasted by ether so that could be it. I will check them after I run the rest of the fuel out & see what they look like. That should be another couple hours of time.

 

[JW in Texas]

OK, I think we can definitely rule out vapor lock. I did both the booster pump & EFI return mod, same issue. Took it out this afternoon, ran her for about an hour, brought her back to the dock, idled for 10 min, ran blower another 10 after shut down(and entire time we were out on the water),let her sit 40 min and no start. She kind of bumps when you first crank then that is it & when I say kind of I mean barely a grumble. Tried cranking with the throttle wide open for a bit, but no love. Pulled the plugs, threw in a new set & bingo, fired right up. Plugs had a slight smell of fuel, but were not what I would call soaked. Obviously, it was enough though. Anyway, it appears she is fouling the plugs upon initial attempt to hot restart. Temp sensor for the ECU is within spec and voltage varies with engine temperature as it should so I think the ECU is getting good info on whether it is a hot or cold start. Could this be an IAC problem? Never had idle issues, but I am running out of options. HELP! Thanks guys,

 

[alldodge]

When it wont start does the tach come up to at least 300 rpm?

 

[JW in Texas]

That is of course the one thing I forgot to check yesterday in all my frustration.i will have to take her out again & duplicate the issue.

 

[JW in Texas]

alldodge,
Still chasing this thing. I got it to no-start today & it is only hitting 150-175 rpm during cranking on the MEFI reader. Also noticed that voltage drops to 10.5 or so. I bought a MEFI reader from Bob at OBD Diagnostics so I have a few good files of when it starts & runs great & from today when it wouldn't start. I don't know enough about the data to mine any info, but if somebody has Bob's software & is familiar, i could really use some help. I am running out of mechanics, I have done a bunch of stuff myself as can be seen above & the dealer is at a loss. I am wondering where to turn next. Crazy thing is when it starts, it is immediate & it runs great. Thanks for hearing me out, just very frustrated.

 

[JW in Texas]

When it wont start does the tach come up to at least 300 rpm?

Still chasing this thing. I got it to no-start today & it is only hitting 150-175 rpm during cranking on the MEFI reader. Also noticed that voltage drops to 10.5 or so. I bought a MEFI reader from Bob at OBD Diagnostics so I have a few good files of when it starts & runs great & from today when it wouldn't start. I don't know enough about the data to mine any info, but if somebody has Bob's software & is familiar, i could really use some help. I am running out of mechanics, I have done a bunch of stuff myself as can be seen above & the dealer is at a loss. I am wondering where to turn next. Crazy thing is when it starts, it is immediate & it runs great. Thanks for hearing me out, just very frustrated.

 

[alldodge]

I got it to no-start today & it is only hitting 150-175 rpm during cranking on the MEFI reader. Also noticed that voltage drops to 10.5 or so. I bought a MEFI reader from Bob at OBD Diagnostics

Could be there is a battery or cable issue, because the voltage if accurate is to low to start. The ECM needs higher voltage to keep it working. The lower rpm rate is also an issue

I have MEFI burn package which comes with scanner pro from Bob but what is the reader you have

 

[JW in Texas]

Could be there is a battery or cable issue, because the voltage if accurate is to low to start. The ECM needs higher voltage to keep it working. The lower rpm rate is also an issue

I have MEFI burn package which comes with scanner pro from Bob but what is the reader you have

I have his MEFI reader which outputs his . xdl files. I bet yours would open them. Can you take a look at them if I email.

We did new batteries, no change, but since this only happens when hot, do you think the starter could be pulling too much juice when heat soaked causing the low voltage & slow rpm turnover speed.

 

[alldodge]

We did new batteries, no change, but since this only happens when hot, do you think the starter could be pulling too much juice when heat soaked causing the low voltage & slow rpm turnover speed.

Could be, its not turning over fast enough

The xdf files are the definition files, would need a xdl file

Make a copy and remove the extension then see if it can be attached

 

[JW in Texas]

Could be, its not turning over fast enough

The xdf files are the definition files, would need a xdl file

Make a copy and remove the extension then see if it can be attached

You are right, they are .xdl. I tried to upload without an extension & it errored. Tried adding a jpeg & txt extension & it errors saying content does not match data in file. If you want to email me at: royalbcat@aim.com I can reply with the files if that works for you. Thanks!

 

[alldodge]

Your IAC position is over 130 and should be around 40 when idling during cold start. Once warmed up and idle comes back down the counts get better but then come back up.

The voltage never gets much above 12.4V for any length of time except one time and then it was 13 something. Voltage running should be 14,5V

Need to get the voltage correct first, then other things may start to settle out or at least show what the issue is.

When it doesn't start I'm seeing 10. something volts

Just to make sure you are using Mefi3 xdf file when running scan (your motor would have a MEFI 3)?

 

[JW in Texas]

Your IAC position is over 130 and should be around 40 when idling during cold start. Once warmed up and idle comes back down the counts get better but then come back up.

The voltage never gets much above 12.4V for any length of time except one time and then it was 13 something. Voltage running should be 14,5V

Need to get the voltage correct first, then other things may start to settle out or at least show what the issue is.

When it doesn't start I'm seeing 10. something volts

Just to make sure you are using Mefi3 xdf file when running scan (your motor would have a MEFI 3)?

Yes, using Bob's MEFI3 file, it is the only one he sent me. I am going to meter all the battery cables, connectors & grounds for resistance & see if I can get readings on what the starter is pulling in cold & hot cranks. I remember from my BB hotrod days that they hate hot starts. Thanks again!

 

[Offthepath]

I had a hard start issue that was very similar to yours. One of the members here said it needed at least 300 rpm to fire. Turns out it was cranking slow and generally it was only turning 250-275rpms

I only had 4g wiring going to the battery switch and probably the main issue, the crimp on lug for the main starter cable was loose. I replaced the lug, ran 1g cable from both batteries and it now starts right up when warm. Cranking rpm now is 400+

 

[JW in Texas]

I had a hard start issue that was very similar to yours. One of the members here said it needed at least 300 rpm to fire. Turns out it was cranking slow and generally it was only turning 250-275rpms

I only had 4g wiring going to the battery switch and probably the main issue, the crimp on lug for the main starter cable was loose. I replaced the lug, ran 1g cable from both batteries and it now starts right up when warm. Cranking rpm now is 400+

That's good to hear After all we have tried, new cables &/or a starter would be an easy fix. Some poking around with my multimeter should reveal a lot. The starter & cables are 20 years old & the marine environment, even fresh water takes it's toll. It's a high humidity cooker in these engine compartments.
​​​​​

 

[JW in Texas]

Your IAC position is over 130 and should be around 40 when idling during cold start. Once warmed up and idle comes back down the counts get better but then come back up.

The voltage never gets much above 12.4V for any length of time except one time and then it was 13 something. Voltage running should be 14,5V

Need to get the voltage correct first, then other things may start to settle out or at least show what the issue is.

When it doesn't start I'm seeing 10. something volts

Just to make sure you are using Mefi3 xdf file when running scan (your motor would have a MEFI 3)?

Did some testing this morning. Cables look like new 1/0 & the connections are all clean. I have no voltage drop on either side between the batteries, Perko switch, ground block, engine block or starter. The voltage drops to 11.2 on a cold start & from data it looks like around 10.5 when it is hot & doesn't start. I am leaning towards the starter, but I don't understand why twice when it didn't start hot, I quickly put in fresh plugs & it fired right up. I can understand that 150 rpm is too low to start and so the plugs then foul, but why when the motor is still hot with new plugs 30 min later it fires. New plugs aren't going to make a hot motor with a dragging starter spin faster. I would think it would just foul the plugs again since it is still hot. The attached are the data points from Bob's MEFI reader. Both sides are when cranking, right​​ is the no start, left is a good start. What am I missing?

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