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 MPI troubleshooting help
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Author Previous Topic: Lehman 120 diesel will not start Topic Next Topic: 2001 90 HP Johnson steering issue  

alk

RO# 5508

Posted - May 12 2018 :  17:28:20  Show Profile  Reply with Quote
After 12 years with a carbed 350 in my boat, I finally dropped back in a replacement for the original motor, a 7.4 mpi.

I saw the replacement motor start right up and run fine with a test harness when the motor was sitting on a palette. Got it into my boat last week, finished hooking everything up this morning- but can't get it to start.

It will crank. And when first hitting the key it sounds like it's about to fire, but wont. I was thinking fuel, because it does sound so close to starting. But thinking it may be spark, I put a timing light on it - to see if it was flashing.

When I turn the key and motor starts cranking, I get ONE flash from the timing light. Doesn't matter how long I leave the starter cranking, don't get a second strobe.

When I lay off the starter for a second, and try again right away, I do NOT get a timing light flash on next attempt. But if I wait about 5-6 seconds, until after I hear a relay located on the back of the coil 'click', now I do get the one flash when cranking and the cylinder fires, but again continuing to crank never get another spark to the cylinder I'm hooked up to.

I thought I had everything wired correctly, with all my grounds good. If I had no crank, or no spark ever - I would assume I missed something on the hookup. But it's like something is tripping to protect the motor by shutting of spark, a second or two after I start cranking.

love the whole MPI / ECM system when it's working, but really in the dark trying to troubleshoot this. Anybody have any ideas who these things work? thanks.

Homeport: PA

walterv

RO# 12640



Posted - May 12 2018 :  19:07:47  Show Profile  Reply with Quote
Alk,

Guess as you know you need to determine if it is "spark" or "fuel". Try pulling a spark plug to see if it is wet (smells like you have fuel). I am not sure if you can do this, but maybe you can shoot some ether(SP) into the throttle body? Wait to hear from others before you do that. To check for spark, I assume you can pull a spark plug wire and use the old screwdriver deal to check for spark. Unfortunately, I am not knowledgeable on MPI, but just shooting out some ideas.

Walter


And always remember, life is not measured by the number of breaths we take, but by those moments that take our breath away.

George Carlin

Homeport: Go to Top of Page

alk

RO# 5508

Posted - May 12 2018 :  20:15:55  Show Profile  Reply with Quote
I can pull a plug, but the fact that the timing light flashes at me as the motor is spinning, but only one time, has me pretty sure I will also see one spark.

My guess is that there is some kind of shutoff in these ignitions that kills the spark if it senses some other condition - and I am for some reason sensing this condition. But just a guess; trying to research online, but looking for an expert as I'm not finding much.



Homeport: PA Go to Top of Page

cmariner32

RO# 7269

Posted - May 12 2018 :  23:45:14  Show Profile  Reply with Quote
Only one flash on the timing light makes it a spark issue. Not being adept with all this new technology (I still have a rotary dial cell phone) methinks either a wiring issue or the ECM-if you have one-needs looked at. The relay clicking would be the first thing to look at-what controls that? Keep us updated on what you find.

The only thing that works on an old boat.....is the Owner.

Homeport: Clearwater/St. Pete Florida Go to Top of Page

Sandy

RO# 1159

Posted - May 13 2018 :  02:41:32  Show Profile  Reply with Quote
Could the clicking relay be related to lower voltage getting to the ECM during cranking, shutting it down and removing voltage from devices the ECM controls like ignition and fuel pumps, injectors,etc. ? Starter causing excess voltage drop with high current
? Maybe replace the on-engine fuse for the ECM even if it looks & tests OK?

Or possibly the ECM is not detecting signal from the CKP/crank position sensor ? But if that were the case I wonder why you get the one spark. Speaking of which , if you put the timing light pickup on the coil wire instead of a plug wire ( if that's where you tested) , do you see any add'l flashes at all?

Does the oil pressure gauge move up at all when cranking? Oil level rechecked on proper dipstick for that application and good after oil has circulated slightly ( filling remote filter and lines)? Is battery fully charged and testing Ok? Any lanyard kill sswitch key in place?


On a tangential note, the jump from 5/7L carbed to 7.4L MPI offers a lot of potential for fun . Just wondering if you upgraded transmission ( if I/B) to handle the big jump in torque, and increased exhaust hose , muffler and transom exhaust ports's size to handle the increased air flow to prevent excess back pressure? None of that would be causing the 1 spark predicament.

A marine diagnostic scan device with proper adapter... could ...save a lot of guessing , even to help rule out many suspects. Sooner or later (like now), with an MPI engine you are likely going to want to invest in one and the ignition diagnostic manual. That said , I'm not sure how much data an attempt at a scan will provide with ony 1 spark while cranking.

Do you have a service manual with wiring diagram yet?

What is the back-story on this 7.4L MPI? Year/model/rated hp/ser.# if Merc. ( for parts check)?
Is a new turnkey engine , or used/rebuilt/remanned?? What all did you have to add or wire up?
Does it have the Delco EST distributor , or flat-top cap on a "high voltage switch" that looks just like a distributor, or distributorless ignition?

Disclaimer: Justaboater


Sandy

Homeport: The Vineyard Go to Top of Page

boatbum

RO# 36

Posted - May 13 2018 :  06:39:13  Show Profile  Reply with Quote
If you have not, check the wiring again looking for bad connections. Were any sensors used on the test rig removed and replaced with your own?


Homeport: Go to Top of Page

alien1952

RO# 32487

Posted - May 13 2018 :  11:58:20  Show Profile  Reply with Quote
Do you hear the fuel pump cycle when the key is turned to "on"

aka Bt Doctur

Homeport: nj Go to Top of Page

alien1952

RO# 32487

Posted - May 13 2018 :  12:02:53  Show Profile  Reply with Quote
I can have a guy burn #23 and #33 if you cant find them

aka Bt Doctur

Homeport: nj Go to Top of Page

alien1952

RO# 32487

Posted - May 13 2018 :  12:04:08  Show Profile  Reply with Quote
I saw the replacement motor start right up and run fine with a test harness when the motor was sitting on a palette. Got it into my boat last week, finished hooking everything up this morning- but can't get it to start.

Was the test harness wired the same as you harness plug, do you have a serial number of the replacement motor?


aka Bt Doctur

Homeport: nj Go to Top of Page

alk

RO# 5508

Posted - May 13 2018 :  16:13:29  Show Profile  Reply with Quote
rainy day today, didn't have much chance to look at anything - but I did look around again for loose wires, burnt or missing fuses - and didn't find anything. Trying to start today, same thing. Turn on the key and the fuel pump cycles, plenty of fuel pressure as evidenced by the fuel which sprayed all over me when I checked the shrader valve at end of fuel rail. With timing light inductor on coil wire I get 5-8 quick flashes when motor starts cranking, really sound like it's going to fire but then spark cuts out. Wait 5-10 seconds, relay clicks, fuel pump cycles on - and ready for another 5-8 sparks.

The motor has the standard merc 10(?) pin plug. The shop I bought the motor from had a key-switch he plugged into the harness, and cables from the battery to back of starter and block. That was it. I must have broke or blown something when I installed the motor - I have same harness, plugs right in. I know this boat is wired / fuel plumbed / geared, etc correctly for this motor - as it's the identical setup I had when I bought the boat new in 1999. When I put the small block in in 2006, all I changed was the props.


Motor serial number is 0L028306. This was a 'running take out' used motor from some guy who had it in a Formula that he barely used. He died, boat wasn't worth much because vinyl, canvas,and everythign else was very worn - but motor ran great. Scan tool showed about 450 hours when we ran it in the shop.

i have the clymer and seloc books, I think boatfix.com has the merc manuals online still? The factory manuals are great, but they operate under the assumption you have all of the merc diagnostic tools, which I don't.

I am leaning towards pulling the motor back out, and taking it back to the shop I bought it from. Not ideal, but he has all of the scan tools ( which are freaking expensive) -- so hopefully he can get it running on the pallet again. He did tell me I could bring it back if I had any problems. Or maybe I will tow the boat up there, and see if he can fix it still in the boat ( that probably won't be free though). Left them a message Saturday, hopefully will be able to talk to them Monday.

The smallblock I pulled still runs fine - I picked up a straight inboard ski boat this winter that had a blown motor. Plan was to put the SBC into the ski boat, and then get a rat motor back into the bowrider. But summer is coming, worst case, I will just drop the carbed 350 back in, and forget about the ski boat until I get the 454 straight.



Edited by - alk on May 13 2018 16:16:58

Homeport: PA Go to Top of Page

Sandy

RO# 1159

Posted - May 13 2018 :  16:52:44  Show Profile  Reply with Quote
The culprit is in here somewhere :

http://www.marineengine.com/parts/mercury_marine_parts/sn/0L028306/4542067LS/2705_60

I once had an MPI engine that wouldn't start but cranked fine. Turned out there was a very slight, very hard to discern bend in one of the fuel pump relay connector pins . Once that was straightened and connector reconnected, the fuel pump energized and the engine started right away when key was turned.
So you might check each connector that was apart and look realllly carefully for anything that might be amiss.

You could try temporarily disconnecting the OP switch leads too.

The #94070 Rinda Techmate Pro kit is about $500 with one adapter, straight from Rinda. Rinda at least used to be happy to swap out the usually included 94005 adapter ( for GM MEFI ignitions ) for the 94006 adapter which I ...think... would be appropriate for your Mercruiser EFI (MPI) engine's diagnostic connector ( but check with Rinda if interested in a purchase.)

http://www.rinda.com/acro/TechMate_Pro_Specs.pdf

What would one visit to the shop for them to scan likely cost you? And you can't keep the shop tech with you on the boat. Well, not for $500, right?


Sandy

Homeport: The Vineyard Go to Top of Page

boatbum

RO# 36

Posted - May 13 2018 :  17:58:01  Show Profile  Reply with Quote
If it boils down to taking it to the mechanic, take it in the boat. Otherwise you could wind up right back here after the test.


Homeport: Go to Top of Page

alien1952

RO# 32487

Posted - May 13 2018 :  18:41:10  Show Profile  Reply with Quote
the engine plug should be a match to yours. Did the PO/mechanic use a harness or just jumper wires on the motor plug?

aka Bt Doctur

Homeport: nj Go to Top of Page

alk

RO# 5508

Posted - May 13 2018 :  19:43:35  Show Profile  Reply with Quote
he had a 'homemade' harness.


Homeport: PA Go to Top of Page

alien1952

RO# 32487

Posted - May 14 2018 :  10:57:35  Show Profile  Reply with Quote


check to see if you have 12v at the Red wire at the coil with the key on


aka Bt Doctur

Edited by - alien1952 on May 14 2018 11:00:08

Homeport: nj Go to Top of Page

alk

RO# 5508

Posted - May 14 2018 :  16:07:37  Show Profile  Reply with Quote
found a local shop that let me rent their scan tool - showing two errors code 42 - EST System Gounded. and something about low oil pressure telltale has been set. Which I don't think tells me anythign useful.

I am going to pull the motor back out, and see if I can get it running on the stand again. The access in this boat is so tight that it's almost less work to pull the motor first just to change the starter.



Edited by - alk on May 14 2018 16:54:35

Homeport: PA Go to Top of Page

Gregory S

RO# 2620



Posted - May 14 2018 :  19:20:21  Show Profile  Reply with Quote
Can you start it with the harness used when on the stand while the motor is still in the boat?


Homeport: Norfolk, Va Go to Top of Page

cmariner32

RO# 7269

Posted - May 14 2018 :  23:26:44  Show Profile  Reply with Quote
Taking it to a knowledgeable mechanic and having him troubleshoot the problem HAS to be cheaper than pulling the engine...putting in on a stand and trying to see if anything is wrong. You need the problem sourced and fixed in your boat-not on a stand. Then again, if you have more money than yanno what to do with, I have a boat that could use a cash infusion.

The only thing that works on an old boat.....is the Owner.

Homeport: Clearwater/St. Pete Florida Go to Top of Page

alk

RO# 5508

Posted - May 14 2018 :  23:59:18  Show Profile  Reply with Quote
It wasn't my harness, belonged to the shop where I bought the motor - several hours from home. But I did order a male 10 point merc plug yesterday that I can use to build my own harness. I think I have an extra tach, temp and oil pressure gauge somewhere in my garage - so I should be able to rig up a pretty cool little harness - just need to find an ignition switch , or I suppose a toggle and pushbutton.

Finding a knowledgeable mechanic ( or even a clueless one) willing to look at a boat around here, this time of year, is pretty much not possible. At the Mercruiser shop close to my house, where I go for a lot of parts, I looked in the shop yesterday, they had so many boats in there it was hard for them to even walk around. I asked them how backed up they were in service as I needed some work done - he just laughed. If I leave my boat tomorrow, no guarantee they would be able to look at it before end of JULY! There were two other decent shops in my area - one of them closed a few years ago when they leveled the whole block to put in a Courtyard Marriott, and the other stopped doing service and only sells parts now. Most of the marinas near the beach stopped doing service years ago - only a few left and they are expensive and busy

Trying to pull off a double engine swap on the cheap, starting in late April, was not the wisest move I ever made -- but no regrets yet.

The benefit of pulling the motor is that if I ( or the guy I bought it from) can't get it running right again on the pallet -- I drop the small block back in, and I'm ready to go boating. If it does run right, I will know that the problem is on the boat, not the motor. I know, not the most efficient way to diagnose a problem- but considering I can't even see the front or back of the motor once it's in, and I couldn't afford to pay someone competent to fix this thing even in the impossible event I found someone willing to look at it -- if the new harness I make doesn't get it started, motor is probably coming out one evening later this week.

Pulling the motor is surprisingly easy - and since I haven't aligned it or put the drive back on yet, now would be the time to do it.

Getting a little worried by the 42 fault code it's throwing, my limited online research says to replace the ignition control module and/or ECM. If I have to replace both of them, that's about more than I paid for the motor - so I may go another direction.



Edited by - alk on May 15 2018 00:11:06

Homeport: PA Go to Top of Page

dkjbama

RO# 25654



Posted - May 16 2018 :  17:26:24  Show Profile  Reply with Quote
Start simple and cheap. If the boat has a kill switch lanyard, ensure it is attached. I stranded myself for an hour once with your symptoms because the lanyard end was halfway off the kill switch.

DKJ in Alabama

2002 Lowe 19' Deep-Vee FM195WT
_________________________

"People do weird things to boats" - Unknown

Edited by - dkjbama on May 16 2018 17:27:06

Homeport: Wilson Lake, Tenn. R.at Florence, AL Go to Top of Page

alk

RO# 5508

Posted - May 16 2018 :  20:26:11  Show Profile  Reply with Quote
On my boat when the lanyard is pulled or even loose I get no power to crank, nothing on the dash volt meter, and nothing at the coil to deliver a spark. I am getting plenty of crank, 12.5+ on the volt meter, and spark for 1-2 complete engine revolutions. Then something tells the ignition relay to trip, and no more spark.

Two deliveries are on their way to my house - a replacement ignition module - which is somewhat of a hail mary, but at 80 bucks figured it was worth a try. And a merc ten point plug so I can power the starter and ignition without depending on boat wiring and ignition switch. Actually I could jam a wire into the boat end of the 10 point plug to accomplish the same, but figured it would be cleaner- could even go boating if it comes down to it- with the homemade harness. If neither of these get it done, I'll need someone with actual skill and experience to fix it. So will have to decide if I want to put the 350 back in for June boating, or just trailer it somewhere and wait until they can fix it.

Man, those ECM's are pricey. I wish I would have kept mine when the original 454 bit it 12 years ago. I sold it on ebay, don't think I got more then 200 for it. These days they run at least 600, as much as 1,500. It's a delco part, would think an auto one would work, but I guess not?



Homeport: PA Go to Top of Page

Sandy

RO# 1159

Posted - May 17 2018 :  01:57:10  Show Profile  Reply with Quote
Something sounds odd about your lanyard kill switch setup .

I've never heard of one that will not allow the engine to crank if the lanyard key is removed . I believe it should only open the ignition circuit on both Run and Start ign key switch positions ( or close that circuit to ground it out on older 2 cycle O/B's), not affect the starter circuit , so it should still crank but not fire .

But maybe yours is different by design?


Sandy

Homeport: The Vineyard Go to Top of Page

alk

RO# 5508

Posted - May 17 2018 :  07:36:00  Show Profile  Reply with Quote
mine's always been this way - when it's pulled, no power to anything on the dash, so motor can't crank.

Does anyone actually wear their lanyard? I know I'm supposed to, and I think 15+ years ago I used it maybe once or twice. But can't remember last time I clipped it on. Remember plenty of times the boat wouldn't start, or stopped dead while running because it came loose.

Fedex drove around all day yesterday with my ignition module in their truck, but never attempted to deliver. Maybe today.



Edited by - alk on May 17 2018 08:30:25

Homeport: PA Go to Top of Page

Cam

RO# 1558



Posted - May 17 2018 :  09:05:03  Show Profile  Reply with Quote
Only time I wore the lanyard was when I was alone in the boat.

" If you think nobody cares, try missing a few payments " (author unknown)

Homeport: Bentley Yacht Club- Staten Island, NY Go to Top of Page

GeeBee

RO# 385



Posted - May 18 2018 :  15:38:34  Show Profile  Reply with Quote
alk, you have a PM.

"The trouble with socialism is that you eventually run out of other people's money."... Margaret Thatcher

Homeport: Lake Lanier, GA Go to Top of Page

alk

RO# 5508

Posted - May 18 2018 :  21:41:03  Show Profile  Reply with Quote
thanks everyone for your help, but I am about ready to throw in the towel on this motor and take it to a shop ( out of the boat), throw my small block back in, and perhaps swap them in a month or two depending if the 7.4 is usable. I took a chance on a running take out, have had some luck in the past with three others I purchased for various boats, but it's not looking great this time. I actually had it running for about 10 minutes this evening, it was idling ok, restarted a few times with no issues, thought my new ignition module did the trick. Then I tried again after about 30 minutes, now I can't get it to start. Different problem though, now I am getting plenty of spark without cutting out, but won't start up. Fuel pressure at the end of the rail is 40-45, but cylinders don't appear to be getting the fuel. hate computers. give me back a damn carb and some points!


Homeport: PA Go to Top of Page

Sandy

RO# 1159

Posted - May 18 2018 :  23:26:51  Show Profile  Reply with Quote
Soooo close!
Have you tried starting with the throttle lever all the way to WOT in order to shut off the injectors, just in case there is a flooded condition? Possibly with a quick shot of gaseous starting fluid to minimize add'l cranking?

Rechecked the ECC/ECM on-engine fuse? Gas itself is good quality / fresh?

Personally , I would really hate to ever regress back to carb , points, condenser and ballast resistor.


Do you think there is any chance the seller could have swapped back out the ignition module and possibly computer after the test run, in order to save the good ones for his other motor or other use?



Sandy

Homeport: The Vineyard Go to Top of Page

alk

RO# 5508

Posted - May 19 2018 :  14:48:32  Show Profile  Reply with Quote
I don't think the seller swapped the ECM, but not 100% sure. When he ran it at the shop I remember being glad it was under 500 hours on the motor, and thought it was 477. And now it's showing 466. Perhaps I got the number wrong - I suppose more likely than him swapping ECM's. But that thought has entered my mind, as I did not take the motor the same day I saw it run. I trust the guy, but I'm a dumbass who trusts everyone.

Anyways, this morning I went over to the shop to return the scan unit he let me borrow/rent. He asked if I changed the coil yet. At nearly 200 for the mercruiser coil, that was a part I had not thrown at the problem yet. I was sure since there was enough current in the wire to fire the timing light that I had spark. Apparently big mistake on my part. He couldn't talk me into buying one, but he had a loaner coil in the back that he let me borrow. Brought it home, after trip to store for a 12 point 3/8" socket ( why mercruiser?), engine fires right up! I guess I'm going to go try it again every 30 minutes, and see what happens -- beer after every time it starts, shot if it doesn't?




Homeport: PA Go to Top of Page

Sandy

RO# 1159

Posted - May 19 2018 :  23:57:44  Show Profile  Reply with Quote
Well I sure hope that really did fix it "reliably", but whether or not that is the case you must be feeling pretty happy by now. (7hrs x 2beers/shots per hour....)

Not sure how accurate this is for MPI high energy coils, but suggest you test both old and "new" coil primary and secondary circuit resistance to see how much the coils differ from each other.
http://www.boatered.com/forum/topic.asp?TOPIC_ID=51465


Sandy

Homeport: The Vineyard Go to Top of Page
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