Any MEFI 3 experts?

[Jonas Grumby]

I have a Teague 875 based 509. With twin whipples. Running on the mefi 3 that the original 500efi ran from 2003. Engine only has 100 hours. Tuned by Brian Macy. This year it has decided to be very very tough to start. Idles fine, runs like a raped ape. It will start right up when warm, but first start of the day, you almost give up and go home. If you sit and float for more than let’s say 30 minutes, it’s tuff to start, but not as bad as first start of the day.
It’s got plenty of battery, due to it turns over and over and over. I’m afraid I’m going to burn up the starter.
I’m thinking there is some circuit that turns on, or needs to turn on for starting.

Any guesses?

 

[mattyc]

I have a Teague 875 based 509. With twin whipples. Running on the mefi 3 that the original 500efi ran from 2003. Engine only has 100 hours. Tuned by Brian Macy. This year it has decided to be very very tough to start. Idles fine, runs like a raped ape. It will start right up when warm, but first start of the day, you almost give up and go home. If you sit and float for more than let’s say 30 minutes, it’s tuff to start, but not as bad as first start of the day.
It’s got plenty of battery, due to it turns over and over and over. I’m afraid I’m going to burn up the starter.
I’m thinking there is some circuit that turns on, or needs to turn on for starting.

Any guesses?

This is a new condition? Did it used to start ok after sitting? Are you able to monitor fuel pressure?

 

[Jonas Grumby]

This is a new condition? Did it used to start ok after sitting? Are you able to monitor fuel pressure?

yes, new condition. Fuel pressure is good and holds during cranking. Runs great, once running. After it’s been running, and you try to start with ing about 30 minutes, fires right off. Wait 45 minutes, and it’s a hard start. Wait a day, and I feel lucky I get it to start. This is new this season. It’s always been a little cold blooded on the first star of the day, but any time after that, it was just a tap and she fired off. Even if we had been floating for 3-4 hours. I put new cap and rotor in early last year, I’m going to look in there, but don’t expect to find a cause. I have to take the blower intakes off, they hang over the distributor, kinda a bitch to work back there.

 

[Teague_JR]

I have a Teague 875 based 509. With twin whipples. Running on the mefi 3 that the original 500efi ran from 2003. Engine only has 100 hours. Tuned by Brian Macy. This year it has decided to be very very tough to start. Idles fine, runs like a raped ape. It will start right up when warm, but first start of the day, you almost give up and go home. If you sit and float for more than let’s say 30 minutes, it’s tuff to start, but not as bad as first start of the day.
It’s got plenty of battery, due to it turns over and over and over. I’m afraid I’m going to burn up the starter.
I’m thinking there is some circuit that turns on, or needs to turn on for starting.

Any guesses?

Since it cold started decently before and now it doesn't want to this season, I would say its not related to the ECM or tune. Might not be a bad idea to send the injectors out for sonic clean and flow bench test. Check base timing, check all sensor voltages and operation with key on. Might be distributor module providing a crap signal at low cranking RPM...

 

[Teague_JR]

yes, new condition. Fuel pressure is good and holds during cranking. Runs great, once running. After it’s been running, and you try to start with ing about 30 minutes, fires right off. Wait 45 minutes, and it’s a hard start. Wait a day, and I feel lucky I get it to start. This is new this season. It’s always been a little cold blooded on the first star of the day, but any time after that, it was just a tap and she fired off. Even if we had been floating for 3-4 hours. I put new cap and rotor in early last year, I’m going to look in there, but don’t expect to find a cause. I have to take the blower intakes off, they hang over the distributor, kinda a bitch to work back there.

might be the Inlet Air Temp sensor or Coolant Temp Sensor not operating properly and thus not providing proper cranking enrichment

 

[Jonas Grumby]

might be the Inlet Air Temp sensor or Coolant Temp Sensor not operating properly and thus not providing proper cranking enrichment

This is what I’m thinking, something that is needed for “cooler” start. Maybe I should try a squirt of fuel in the intake and see if it fires, might get me aimed in the right direction.
The motor has treated me well, we put it in in 2017. Like I said once running everything is fine, I clicked off a buck 15 this morning before the crazy’s got launched.

 

[Jonas Grumby]

might be the Inlet Air Temp sensor or Coolant Temp Sensor not operating properly and thus not providing proper cranking enrichment

Do you know where the air temp sensor is on a quadrotor? I would assume behind the throttle blades, but I see no electric connection there. Only plug in that area is the throttle position sensor.

 

[Teague_JR]

Do you know where the air temp sensor is on a quadrotor? I would assume behind the throttle blades, but I see no electric connection there. Only plug in that area is the throttle position sensor.

Its in the intake manifold near the distributor. 3/8" npt brass sensor with a 2 wire plastic delphi weatherpak connector. Very common for them to get crispy.

Its reading the air temp after the intercooler.

you really need to throw a scan tool on it and give it a quick once over.

 

[Jonas Grumby]

Its in the intake manifold near the distributor. 3/8" npt brass sensor with a 2 wire plastic delphi weatherpak connector. Very common for them to get crispy.

Its reading the air temp after the intercooler.

you really need to throw a scan tool on it and give it a quick once over.

Thank you sir.

 

[Jonas Grumby]

The temp sensor reads 3.5v at ambient temp in the garage about 77 degrees. Google says 3.5v is 68 degrees. So I don’t know for sure but maybe this sensor is a bit off.
But if it’s the issue, it should be supplying enrichment.

I squirted some gas in the blower, no differance, no start.

 

[Fun Times]

Every once in a while, there are some places on eBay that will rent a Diacom scanner set up for marine engines if interested.

Rinda Technologies, Diacom Rental for sale | eBay

Get the best deals for Rinda Technologies, Diacom Rental at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

 

[Jonas Grumby]

Every once in a while, there are some places on eBay that will rent a Diacom scanner set up for marine engines if interested.

Rinda Technologies, Diacom Rental for sale | eBay

Get the best deals for Rinda Technologies, Diacom Rental at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

will that scanner tell you, hey you need a xxx sensor?

 

[Fun Times]

will that scanner tell you, hey you need a xxx sensor?

That would depend on what is the exact issue… If the sensor was to far out of range of normal to either the high or low side of max / minimum value, it will create a fault code telling you what one is bad.

That mentioned of being to far out of range, you’d generally may get a warning horn too such as say the connector being unplugged.

But should the sensor be say slightly bad (which is more to the rare side but not impossible) though not above or below the default ranges the ECM is looking for to set codes, that would be where having the scanner helps alleviate the sensor value ranges of being possible bad but not quite past the default range in-turn giving off false needed parameters to adjust fuel settings, etc. and not setting codes… In which you are doing about the same via the multimeter and searching voltage number comparisons to temperatures, etc.,

So while the scanner might not tell you directly what is wrong, it could help tell you what’s right to lower your chasing of the EFI system.

The scanner is generally a helpful tool to start out with when nothing else stands directly out at you.

Should you want to check for codes just to be sure and not want to buy/rent a scanner to use on your/A MEFI system only, here is another way to accomplish checking for their presence using a multimeter,

 

[Liquidkroozir]

when you have the no start,have checked for spark or an injector pulse ?

 

[Jonas Grumby]

when you have the no start,have checked for spark or an injector pulse ?

spark yes. Injector no.

 

[Teague_JR]

If you are getting spark but not injector pulsing while cranking it is likely an ECM issue or harness issue.

Check for 12v on red wire to injectors. Blue and green wires are bank one and two pulsed ground to fire injectors

 

[Jonas Grumby]

“Might” have found the issue or a issue

**EDIT** 99% sure it’s fixed. I think I was sent the wrong rotor last year, it had about a 1/4” gap from tip to cap terminals. All that carbon you see conducts electricity. So all kinds of arcing going on it there. Installed new MSD cap and rotor. I just let the boat sit in 70 degree garage for 4 hours, just bumped the key and she starts. Seems back to normal.

 

[mattyc]

“Might” have found the issue or a issue View attachment 1235946 **EDIT** 99% sure it’s fixed. I think I was sent the wrong rotor last year, it had about a 1/4” gap from tip to cap terminals. All that carbon you see conducts electricity. So all kinds of arcing going on it there. Installed new MSD cap and rotor. I just let the boat sit in 70 degree garage for 4 hours, just bumped the key and she starts. Seems back to normal.

Is the gap you're talking about between the tip of the rotor and respective cylinder terminals? Or between center rotor and center cap? Sounds very likely you solved it

 

[Jonas Grumby]

Is the gap you're talking about between the tip of the rotor and respective cylinder terminals? Or between center rotor and center cap? Sounds very likely you solved it

it was the gap from rotor tip to the cap respective cylinder terminals. MSD says their rotor/cap gap is setup at .075. Kinda hard to measure, you can only center the rotor best you can in the cap and look. But I had a new MSD cap and rotor in my cupboard, and could see a difference in the 2.

 

[farmo83]

it was the gap from rotor tip to the cap respective cylinder terminals. MSD says their rotor/cap gap is setup at .075. Kinda hard to measure, you can only center the rotor best you can in the cap and look. But I had a new MSD cap and rotor in my cupboard, and could see a difference in the 2.

Why would this only affect things when it's cold?

Just trying to educate myself.

 

[Jonas Grumby]

Why would this only affect things when it's cold?

Just trying to educate myself.

IDK

 

[DaveH]

Why would this only affect things when it's cold?

Just trying to educate myself.

when i distributor cap is worn out and carbon traced, spark energy will scatter and go all over. but most importanlty, you get a weak spark to the cylinder trying you are targeting to light.

then add in when the engine is cold and/or hasn't run in a while, there is no residual fuel in the blower meaning a weak/lean mixture during inital crank. when this condition is met with a weak spark......no bueno.

port injection would improve this condtion.

 

[Jonas Grumby]

Ok, new or continued issue. I have no spark. Not at At plugs , then I pulled coil and put near ground, nothing there either. Swapped MSD, box with spare, checked keyed +12v to MSD. checked ground was clean to MSD. I have a MSD PRO HEI distributor, it has a magnetic pickup, checking MSD WEBSITE, That say you can short and open the violet and green wire to send a 12v pulse to the coil. And spark the coil lead to ground. But these wires are not used on my setup? So that leaves the White, that’s use in a points system, I am confused. But it’s they way it always has been from Teague. I checked the new cap and rotor, still look fine. Does anyone know the pin out on the hei? There are 2 plugs, 1 with 2 wires and 1 with 4. The plug with 2 wires is pink and black, I assumed this is the pickup, shorting and open do not spark coil. I tested coil, it’s ok. I hate to do it because of $$$$’s, but I’m going to have to take it to someone it appears.