500EFI Help!
 

500 efi issue. Anybody suggest a test to test an EFI coil output?

One motor started acting up where it would not want to rev past 2500rpm until the boat got on plane, then it was down 200 -300 rpm. A rich fuel smell at idle too. Then a few weeks later, it got worse. Both motors would barely start. Pulled plugs and found all 16 were fouled out. Replaced all 16 and took it out today, one motor started out lazy as before and at the end of the day I could barely get the boat on plane to get home. Again a rich fuel smell at idle. Any thoughts is greatly appreciated. 80 hrs on rebuilt engines. Compression is good and no codes showing on the ECM
I wonder if the coils are going bad. Anybody else have a similar experience with 500 EFIs?

I'd venture to say check the vacuum line to the fuel regulator for cracks.

could be bad coils,i would check the fuel pressure,might be regulators or as earlier mentioned vac hose going bad.also could be water in the fuel,dump the fuel from the filter/water seperator into a clear jar and let it sit.if it contains water the water will go to the bottom of the jar.

true,if both engines are doing something the same,,look for what could be common.may even be corrosion on the ground terminals.start checking.

Thanks everyone for your input. I'll check the ground, fuel pressure and vac hose too and post results.

Fuel pressure was 43psi at idle and dropped a bit to 40psi at 1500.
Checked vacuum lines - no leaks. Checked fuel – no water.
Threw the timing lite on and checked that the ignitions advance as rpms go up.
Also put on my Innovate Air/Fuel meter on one.
12.6 at idle
13.0 1500
12.8 2000
12.5 2500
Here are some pics of the new plugs I put in with less than 2 hrs on them. Only 1 looks halfway normal out of 8.

Anybody have any more suggestions?
[ATTACH=CONFIG]559329[/ATTACH][ATTACH=CONFIG]559330[/ATTACH][ATTACH=CONFIG]559331[/ATTACH]

you could try a new coolant temp sensor. I've seen those go bad, then the ECU sends a pile of fuel to compensate. Might shoot the IAC filter with some brake cleaner, make sure thats not plugged. Thats plenty rich at idle, unless thats an in-gear idle AF.

Good luck-

If you don't have a spare coolant sensor, swap them from motor to motor and see if the problem follows it.

Temperature gauge seems to operate on both motors. Was your gauge working when your ECU dumped fuel in the motor? Wondering if it would still effect the ECU if showing the correct temp on the gauge.

Those plugs are blacker than.......

Time to put a scanner on it and check coolant temp readings as mentioned above, and then tps and so on and so forth.

I check voltage strength to the plugs with a spark plug tester, but you kind of need to see difference of strong spark vs light spark to get an idea.ie: brightness of light blinking

http://www.obd2express.co.uk/upload/...-testerl-1.jpg

I have a Rinda Techmate Pro scan tool but I'm not too experienced with it yet. Do you know what temp parameters should be and how do I check the TPS with it?

Cleaned the spark plugs. Changed the coolant sensors in both motors after the scan showed the coolant temp was 85*
if anyone can help with this - Its still loading up and fouling plugs
I put the scan tool on after a brief run to warm up the engines - Here are the values at idle:

Port Engine
Coolant temp 142*
Manifold air temp 119*
TPS Volts .72
Throttle Pct 1.9
Map Volts 4.09-4.15
Manifold Pressure 25.7
Barametric Pressure 30.4
Battery Volts 12.9-13.0
Spark Advance 12-27 (jumps all around)
IAC Position 140
Base IAC 140
IAC follower 0
Inj Pulse Width 4.9-5.1
Fuel Flow Rate 3.10-3.33

Starboard Engine
Coolant temp 134*
Manifold air temp 117*
TPS Volts .92
Throttle Pct 7.4
Map Volts 3.88-3.94
Manifold Pressure 24.1-25.4
Barametric Pressure 30.0
Battery Volts 14.2-14.3
Spark Advance 13 (steady)
IAC Position 150
Base IAC 140
IAC follower 20
Inj Pulse Width 4.1-4.2
Fuel Flow Rate 2.68-2.85

Do those NGK plugs have gaskets on them ? Sure looks like it. GM cast iron heads use tapered seat plugs. Factory plug is AC Delco MR43T.
Those NGK's also look like they have more threads than the standard Delco plug. Almost looks like plugs you got where like the ones for the 525EFI which uses the NGK BPR6ES that has longer reach threads and a gasket because of the engine having the Edelbrock/Mercruiser aluminum heads.

Here is a pic of factory plug for the 500EFI - AC Delco MR43T - notice amt of threads and also notice tapered seat:
https://images-na.ssl-images-amazon....1edR6s1pPL.jpg

Here is a pic of factory plug for the 525EFI - NGK BPR6ES - notice amt of threads and also notice gasketed seat
https://images-na.ssl-images-amazon....1wNmQz26PL.jpg

Okay, was able to enlarge your pics and you definitely appear to have wrong plugs if you still have the OEM 500EFI heads on your motor. The plugs you have in them appear to have too long of a reach (too many threads) and they are gasketed.

So, it appears that NGK Br6fs is also listed in some 500 efi manuals. Therefore, AC Delco MR43T or NGK BR6FS are the correct plugs.

Edited in my disclaimer: I can not see the NGK # on your plugs. What I have wrote I believe to be true. Please double check my info if you are going to use it. LOL.

Pic of BR6FS for comparison

http://www.marineengineparts.com/med...g/ngkbr6fs.jpg

SB - I have Dart 308 Iron Eagles and they call for 3/4" long gasketed plugs. The motors have about 80 hrs on them since rebuilding and were working fine up to this point.

Okay good !

What a waste of about 1/2 hr of seemingly good detective work on my side. LMAO.

Edit in: Since on the subect, any cam change and ignition 'upgrades' also ?

Thanks SB - It has the 741 cam, AZM throttle bodies, ECM's remapped by Precision Marine, but I don't think those are factors since it was all running correctly for 1-1/2 years

Good stuff.

I understand, but helps with things like MAP readings.

So, no ignition modifications ? ALL OE parts other than plugs ?

Yeah, Stock 500EFI ignition components

Distributor caps and rotors both in good clean shape, with no corrosion or moisture?

i,m not saying this is the case but often ignition problems cause issue,s that get blamed on the fuel system.if the ignition system is weak the fuel can,t get burnt so people blame the fuel system.

Im gonna pull the distributor caps off, inspect and check. Thanks Sydwayz and Mike T for the idea. One other thing worth noting is that the tachs are jumping around above 3000 rpm.

Is there a concern that the advance is jumping around on your port motor scan?

Yes - one motor shows steady at idle, the other is unsteady and ranges all over from 12-27 .

I believe thats the "Idle stabilization" program trying to keep the engine running smoothly.

Checked both distributer caps and rotors. Checked the grounds in the back of the engine. They all looked OK. Man! this has me stumped.
It seems like both motors are in choke mode. Anybody else think of something to check or try?

OK after much troubleshooting, I see that the engine is only producing 7-1/2 – 8 inches of vacuum which seems to be effecting the map sensor. The Map volts at idle is high with engine at operating temp of 140*. With the engine idling, I tried covering the IAC port in the throttle body to see if it would indicate a vacuum leak. Covering the hole about stalls the engine.

RPM / Map Voltage
Idle – 3.80 V
1000 – 3.72 V
1500 – 2.72 V
2000 – 2.11 V
2500 – 2.11 V

500EFI details
525 cam – by Crane – .610/.632 lift 236/242 degrees duration @.050 114* LS
Dart 308 Heads
9:1 CR
AZM throttle body
80 hrs on motors

Compression on each of the 8 cylinders ~120 lbs

With the new information, can anybody suggest what to do next?

OK thanks to everyone who offered advice - the issue turned out to be the modules inside the distributor which were not holding timing. Replaced and solved the issue.

seems strange that the both went bad at the same time.

I suspect the modules were going bad for a while and since the motors still ran and I'm no expert, it was hard to identify. One indicated -2 to +42 at idle on my Rhinda scantool, the other +8 to +22.

MAP at idle is way off it should be 1 V at idle fully warm up engine and about 4.8 V at WOT

I would rescan that for sure

John will scanner show 4.8v with power on and key off? (0 vacuum like wot would be)