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Originally Posted by Gimme Fuel
(Post 4647262)
Fuel pressure is easy to test on these motors and if it is low can cause all sorts of issues. I was chasing a surging idle/hard warm start issue on one of my 2000 502MPI. Motor ran fantastic and was always stronger of two. Threw TPS/IAC at it and no change. I was also having some backfiring occur from what I thought was other engine.<br /><br />Fnally bought a $22 gauge for schrader valve and found regulator was bypassing at 30 psi static. Also found other motor was at 36 psi static. Instantly fixed my starting issues, idle issues, and no more backfiring.<br /><br />It was impressive how well they "sounded" on top end so I discounted having fuel pressure issues and originally leaned to the electronic side of things. Wrong thinking there for sure. Fuel pressure is one of first things I check now if I or a friend have issues.
Have to add all MEFI 3 apps for Merc is 43 psi for fuel pressure. Using a quality fuel pressure tester. Next 4 of the easiest tests to do in the marine world are 1st change all fuel filters and fuel samples - then run the boat / engine on a remote fuel supply with new fuel line and primer bulb to take all that end out of the boat side. If no change move on to fuel pressure testing from key on to the fullest running rpms the engine will perform. Next is sealed inline spark checkers on all 8 hooked while running the engine to watch spark events. . To perform these tests does not cost very much money at all plus one can better determine if the issue(s) are spark or fuel related. 90 bucks for 8 sealed inline spark checkers, 80 bucks for a good 6 gallon remote gas tank - new fuel line - 2 hose clamps and primer bulb - Most gear heads have a fuel pressure testing gauge and a timing lite - if not OTC is a good one to buy for a fuel pressure gauge. . 300 bucks or less will do it. These tests will tell one were the issue(s) are more than half the time. . The remote gas tank is one handy set up to have for boat winterizing properly that can be used many timed for engine lay up.. One can move on with vacuum testing -- compression testing and leak down testing. |
Just want to say first and foremost that I appreciate eveeyone’s help on this. The collection of knowledge on this forum has always been impressive, and for the most part, not a day goes by where I do not learn something new. I think I may have found the issue, or if anything a contributor. Some time you have to go back to the basics. I was going to look at fuel pressure last night, but before doing so I wanted to pull plugs to get a look at overall condition. The plugs looked good, and were what I would expect for having maybe 10 hours on them. While pulling them I found that a couple of the wires on the even bank were burned with one being into the fiberglass where you could see a crack into the core . I had replaced (needlessly) my Merc wires during my tune-up with a 8.8 mm set, and I guess I had a couple touching the header flange. What I’m thinking is that this could have caused some spark scatter inside the cap. I have not pulled the cap yet to see if there’s any damage, but I did put the old wires back on (they tested out fine). Sometimes it can be the simplest of things... back to basics. My alternator should be here today so that should take care of the electrical side of things. I’m off Friday so I’ll make plans to do more testing including fuel pressure, etc. |
One more piece to add, and another reason why I love this forum... Search. Though search on the site can be a little wonky at times, more times then not, you’ll find an answer. I came across a post post from over a decade ago where someone was describing a very similar issue to mine. This person dumped thousands into the trying to fix his MPI set up. In the end it was a set of $50 aftermarket plug wires draped over the ignition circuit wires that ended up causing the whole thing. This place is a treasure-trove of good information. |
Originally Posted by TomZ
(Post 4647475)
<div style="text-align:left;">One more piece to add, and another reason why I love this forum...<br /><br />Search. Though search on the site can be a little wonky at times, more times then not, you’ll find an answer.<br /><br />I came across a post post from over a decade ago where someone was describing a very similar issue to mine. This person dumped thousands into the trying to fix his MPI set up. In the end it was a set of $50 aftermarket plug wires draped over the ignition circuit wires that ended up causing the whole thing.<br /><br />This place is a treasure-trove of good information.</div>
If you go back up read my 300 dollars or less worth of tools to rule out the areas of issues within a couple of hours MAX if that. --- a 90 dollar set of all 8 sealed inline spark checkers would have found his issue within 15 mins or less. PROPER TOOLS are needed if one is going to work on marine apps Just saying --- Tom Z these would have found your spark issues as well within prob the same amount of time. 90 bucks in the sealed inline seal spark checkers or -- my labor rate is 100 bucks per hour pick your battles ? AGAIN DO NOT TAKE this as a slam but positive ways to work on your marine apps. Simple things first more times than not -- more than half the time are the issues --- fuel --- air --- spark --- in both cases were spark here as it sounds like. I am trying to help here not slam ya. Hopefully understandable to get a very solid point across. |
BUP, I don’t see your post as a slam at all. Not even a bit. With that said, I do have the proper tools to work on this thing (well, outside of the spark adapters), and have been doing my own work, exclusively for years and years. I think this situation is different than most; I don’t see the spark plug wire itself being the cause of issues. What I do see is a case where an oddity (spark plug wires too close to the IC wiring) May have been at the root cause of my issues. I don’t think the spark adapters would have shown that (a grounding plug wire yes). This is a special case. The information I found really hit home; it matched pretty much dead-on with what I mentioned in my other thread (bouncing tach needles etc). And this is where the power of the collective knowledge resides. I’m a computer guy (but always a car/boat guy/mechanic since I was old enough to work on stuff), and now run an IT organization within our business. Proper troubleshooting steps with their associated tools are necessary day in and day out so I know the game. Maybe I just don’t convey that via the forum because of the way I ask questions here. But I pretty much made it known that in this case I was looking for some knowledge from those that may have run into this kind of thing before. (I hate my iPhone btw) |
To address BUP's comments it always amazes me the number of people that come onto this forum and ask advice on setting the timing on their boat then comment they cannot afford (read won't spend) the money for a decent timing light, WTF? How the blazes can you set timing on an engine without a timing light? Just saying.
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For many of us it’s a matter of trying not to buy something that will only be used once then clutter up the garage, but what we don’t realize in the beginning is that with boats you’ll always need it again and again and again...:p Forever ago we’d buy a timing light at Sears then return after we were done. The manager was yelling “Dammit that’s the third one today!” Lol. |
Craigslist, that's all I have to say. And Baja I know you own one.
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To know me in person I am not slamming anyone to be clear about this --- really saying deep down I want you to work on your boat easier and faster by all means with as little downtime as possible.. I have said this before I want all boaters to have less problems and get their stuff fixed in a timely manner and back out on the water ways ASAP. Why would I want that for a person who makes money at fixing boat issues inside and out. I want to see people of all ages stay in boating - when working on boats becomes a huge PITA and long timeframes of downtime - those boat owners get out of boating. That would be horrible for everyone including me. NO OFFENSE to anyone.
will say it again 300 bucks in tools listed above ---- even if you use it once can save you way more than that plus your time is worth something to resolve your issues faster.. Heck the way I see it skip one weekend of drinks and buy some tools that you do not have in your box. A quality fuel pressure gauge and YES Glen a quality timing lite are 2 good tools to have in your box. Thats all I am saying -- not pointing anyone out just making broad statements. . |
Originally Posted by BUP
(Post 4647496)
Actually the end was only good info but how long did it take him to find the issue --- months -- years ?? with that said I have to open up my big mouth and please Do not take this wrong anyone --- that is horrible way to go about finding problems --- months on end - crazy parts after parts changing - crazy dart throwing of everything to find issues. This is a prime example of a boat owner for one does not know how to perform testing procedures to pin point issues right away nor had the PROPER TOOLS to find issues.in a matter of minutes rather it sounds like months or years.
If you go back up read my 300 dollars or less worth of tools to rule out the areas of issues within a couple of hours MAX if that. --- a 90 dollar set of all 8 sealed inline spark checkers would have found his issue within 15 mins or less. PROPER TOOLS are needed if one is going to work on marine apps Just saying --- Tom Z these would have found your spark issues as well within prob the same amount of time. 90 bucks in the sealed inline seal spark checkers or -- my labor rate is 100 bucks per hour pick your battles ? AGAIN DO NOT TAKE this as a slam but positive ways to work on your marine apps. Simple things first more times than not -- more than half the time are the issues --- fuel --- air --- spark --- in both cases were spark here as it sounds like. I am trying to help here not slam ya. Hopefully understandable to get a very solid point across. |
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