Shag555

Argh! Anyone ever have one of those days? Was bracing my hand up against the other engine, troubleshooting the other, when one of the injectors broke off!

Thats the least of my worries... Last year, I sucked up some debris, causing the sea pump to lose its impeller. I tore down the cooling system, pump to Oil/fuel cooler to thermostat, and flushed all of the rubber pieces and mud out. This past winter, i also flushed the blocks, so the system is clean, and I've checked the thermostat to make sure that its not stuck open from a stray piece of rubber - it also works at 160f like it should (tested).

When i put it back together, it seemed to run fine, but i had no water temperature at that engine (guage) - the block also seemed to be quite cool in comparison to the other engine. When i put it on the trailer, i noticed black soot all over the transom.

Since this time, I've been reading "what could be wrong" - anything from the Engine Coolant Temperature Sensor (ECT), fuel pressure regulator, etc. I've read that besides sensors, the return fuel screen could be plugged?

Could the overheat have caused the sending unit for the temp guage and the ECT to both be bad? Should I just cut my losses and take this in to a shop (Im doing the fuel injector myself). What would a diagnostics tool (code reader) cost for this engine?

2001 Mercruiser 350MAG MPI

Thanks in advance!

dereknkathy

to start, temp read low, but your hand said temp WAS low. twins. switch temp senders, switch ECT's. but it is probably right. swap thermostat housings. you might need to put it in water. cometimes garden hose pressure-flow rate will not let you see cooling sys issues on trailer.

Shag555

Im going to pick up a Rinda TechMate scan tool. Seems like it could pay for its self rather quickly.

averagejoe074

160 seems kinda low for a mpi engine...its important for these engines to be up to proper operating temp to run correctly...I have a 454 mpi in my boat...temp runs on average 175-180...maybe someone else will chime in with more help..

FIXX

iTrader: (2)

make sure you used the correct t-stat gaskets...if theirs a sensor in the housing their should be 4 brass rivets on the gasket to ground the housing,this will also make the pcm think its still cold and fatten up the mixture because the coolent temp sensor has no reading.

Shag555

This could be my problem... When i checked the thermostat, i sealed it back up with silicone smeared all over the original gasket (sorry fellas this is my first boat).

Both engines show 170F under normal operating conditions.

Perhaps I should put a hair dryer to the sensor to the guage while grounded to the block and see if I get a reading...

larry da outlaw

350 mpi usually have 2 temp sensors, one for the ecm and the other for your temp guage. if you arent reading anything at your gage make sure your r troublshooting the right sensor. as far as your richness issues goes well its an easy one. you need to fix that broken injector first. this is a very very very very (catch my drift) common problem. when an injector goes bad the ecm does not know that (mefi3 or older) so after looking at things such as tps, map and rmps the ecm does knows it has a problem but can only do one thing....save your eng by dumping fuel into the motor to keep it from destoying itself. now a lot more it actually going on here buy I will keep it simple.
also it is possible that you may have more than one bad injector.

Shag555

Thanks for all the input!

Actually, the snapped injector is on the other engine. This ones injectors are fine. The prior gentlemen who owned the boat took very good care of it. On sea trial, there were no issues of the sort. The "no temp / run ruch" problem only arose after the sea pump impeller self destructed, and I made repairs without knowing what the hell I was doing!

I took the goose neck off last night, and, sure enough, the silicone was prohibiting a good ground. I would have figured there would be enough ground through the two 3/8" bolts that clamp down on the goose neck, but, there's enough paint / powdercoat that i could see why that woln't do as ground.

I havent had the chance to test, other than ground the gage thermocoupler to the block, while heating the it with a lighter. It, in-fact, DID produce a reading. That said, the EFI thermocoupler, also known as the ECT, has to read properly or it runs rich (like full on choke mode). In my research here, if these efforts dont pan out, the next suspect is the fuel regulator runs at 80 psi instead of the 40 psi its supposed to be. This is where the code scanner comes in (all these little sensors can get expensive quick).

I havent sea trialed it yet, and my method of "bench running" is to drop the drive in a cattle trough full of water (I have a well). I have the Pittsburgh Marathon to run on Sunday, and after I get that out of the way, I hope to see if the gage comes up, and the rich condition eases. I'll definately need a new set of plugs though too!

One other item, i pulled the gooseneck completely off and discovered a piece of the impeller wedged in part of the webbing on the intake side. Lord knows how much flow this was blocking (10 or 20%?).

Shag555

Actually, in reading my post, i slammed myself. I havent hot rodded in almost 20 years, and there certainly werent a slew of wires to deal with on the SBC's i delt with back then (those were the good old days). Then again, gas was a buck a gallon, and I only had to pay $0.70 because i worked for a penzoil distributor. It really didnt matter how much fuel i burnt back then (typical cruise weekends, id go through 40 gallons)! Today is different, and Im certainly glad I have these little MPI's!

larry da outlaw

fyi, i did not mean that your injectors are broken. i meant to say you must ohm out the injectors and get a reading of 15.5 ohms for your application. anything more or less than 2 ohms should be replaced.