502 Mercruiser - Diagnostics Tool / Program Selection, Experience, Suggestions
 

To all the forum members, first i like to say how well received I have been on the various topics I have asked for help with, thanks to everyone.

I have been searching for the right diagnostics tool for my 1991 Scarab with 2 x 502 Magnum engines.

I do not want to make a costly mistake and get the wrong tools I need.

I am asking for help from the vast forum experience to guide me for the best tool at the best price.

I am not a professional mechanic, but have mechanical abilities and have worked marine engines, so owning the tool is important for me during this restoration and into running the engines for an extended period of time, to have peace of mind knowing if I have any failure at any time I can readily diagnose an issue.

Any insider info from those that have had hands-on experience with these engines would be appreciated. Right now I have a no start issue for 1 engine, I am thinking ECM controller due to some troubleshooting I have already done.

Unless i rule out and identify any codes that may be thrown from the ECM I cannot go forward.

Being a 1991 I would expect to find a carb motor. Are you saying yours is fuel injected? Happen to have the serial number?

Your 502 mag's are MPI models right since your talking about your ECM's. ?? Says 91 Scarab under your name and making sure your not a carb mag engine?

If your MPI, your going to need a Rinda Techmate pro scan tool and 94005 adapter for it

This here has the 94006 and 94006 adapter good for 90+% of anything you need to do. Will scan MEFI1-3 and 555 computer

TechMate Pro - Marine Engine Diagnostic Scan Tool - Michigan Motorz

Also as for a 502 mpi and no start, there pretty basic engine vs the new 555 computer. Fuel, air and spark. Make sure injectors are opening and closing, fuel pressure at the rail, timing is set and you have spark.

1991 had no MPI engines --- 1993 came out with the 502 MPI with VST fuel set up and MEFI 1. Totally waste of money to buy a scan tool with only 7 fault codes for MEFI 1 especially IF the person scanning does not no what all the parameters should be per their marine app. Many times fault codes do not show up but one has to rely on knowing all the parameters per rpms thru out the scan to help pin point possible issues. .

With that said have no idea what ECM is installed to your app. I AM GUESSING MEFI 1 ? ONLY a guess here.

IMO you are better off FIRST to check more indepth of fuel, air, spark, and timing plus the common tune up system parts realted before BUYING A SCAN TOOL - scan tool reads nothing on the fuel side nor is going to tell one about anything spark related for MEFI 1 thru 3. Nor tell you compression nor leak down percentages. Testing the injectors one is better off sending them out as they should be cleaned anyways and tested on a designed machine for that end.

Just one example for a scan tool reading - what would be the correct IAC parameter at dead idle fully warmed up engine using MEFI 1 for a 502 Mercuiser marine OEM stock engine ? If the person scanning does not know that info what good is owning a scan tool. ? Just making an example if one should buy or not buy a scan tool for the app they own. Alot of times people are thinking no fault codes present - my engine sensors / relys / ecm inputs and outputs are all good. Thats not the case at all. Just passing that on for info to possible help ones decision for buying a scan tool for the app they own.

AD,

I am traveling and do not have the ability to get the engine numbers.

EFI engines, this is why I commented ECM, I am not fully engaged [yet] into the requirements for the engines outside of having them recently rebuilt, and they both were running.

Had to shelve the restore project for some time due to travel requirements and now I've gone back to them 1 engine is not starting.

its getting spark, coz I can use starting fluid it and it starts and runs, it seems to be fuel related but the fuel pump is sending fuel, next is the delivery

I immediately see the need for diagnostics after looking at the obvious.

BUP

I commented above about checking the obvious fuel spark etc...

These are EFI's and i dont have the numbers with me and cannot find on emails either.

I'm traveling and taking time to plan forward for getting the engine running when i get home in a couple months.

The engines were rebuilt and running and then laid up in storage for a long time, batteries died, etc....

starting fluid to start the engines do not do that. You need to check fuel pressure thru out. Starting fluid is not a good thing to use spraying thru the intake / throttle body. It is extremely hard on the MAP sensor among other things.

You have a fuel delivery issue to start out with if you are dependent on starting fluid to get the engine to fire off. good luck with it.

I have the Mercscanner (techmate) scanner and Scanner pro. Others also have the Diacom marine software. I like the techmate because its small, portable and rugged. You can see any codes and also running parameters. The down side is to see each item it has to be scrolled thru one at a time.

The Diacom software does the same thing but also displays most info on a laptop screen so several things can be seen at one time, including any codes. Both techmate and Diacom are sold by Rinda. These two items are good but depending on which MEFI you have will depend on how much you can find out when connected.

I mention Scann Pro because it does most of the same thing as Diacom but only comes with MEFIBurn software.

Since you should have a MEFI-1, to read codes all you need is a 12V LED (must be 12V not the cheaper 3V) and a paper clip. Install the LED and paper clip, turn key on (don't start) then start counting flashes. The MEFI-1 has very few codes, the 3 a few more

https://cimg7.ibsrv.net/gimg/www.off...fff24318df.jpg


https://cimg1.ibsrv.net/gimg/www.off...1f59d0362a.jpg

Get a fuel pressure gauge to find out what's at the rail, can borrow one from the local auto store in many cases

BUP, I appreciate your comments genuinely, I used fluid to see if it fired off and did not run with the fluid.

That's when i stopped, assured it had spark, and knew right away I had a fuel delivery prob

I then checked the fuel pump and it was fine

That's when i put the tools down and began researching a diagnostic tool