502MPI rebuild having some issues
 

Hey guys,
Just went out for the maiden voyage of the 27 fountain today and have a couple of issues I could use some advice on.

1997 502MPI rebuilt stock with the exception of CMI headers.
Mefi1 system
All new fuel, timing checked and double checked, fuel system purged and primed.
Code scan showed a MAP sensor fault that was cleared and did not show back up while running on the hose.

Issues:
Idle is very pulsating and seems low. When putting in gear or when backing off the throttle, the motor will die, but will start right back up no issues at all. have to keep it about 1200 to keep it from dying. Doesn't die everytime, but frequently. Docking is difficult this way!!
Issue two: What is a safe oil temp? running 210 at putting around speed, 250 at gentle cruise, but when I ran it up to about 4000 for only a minute, temp was reading close to 310. Is that ok? I fully cleaned the oil cooler before putting back together, and I have a solid 40-60psi oil pressure while running. My water temp is not even getting to 140 on my guage.
There is alot I don't know about this boat, as I bought it in non running condition. I don't know if some of the senders or sensors are bad.

Any help is Greatly Appreciated as always!!

fixx
 

310 is too too hot,you want around 190*..you may have the wrong temp sender for the gauge,always make sure the mfr of the gauge matches the sender..i hope your running a oil cooler? are the lines going in the rite direction? you want the oil to flow the opposite direction as the water flow (X) as for it idleing afu,,how did you check the timing? did you ground the aldl connector? that could be off of you may have a vacume leak..

In response to you idle...have you changed your fuel filter?

I will have to double check oil flow direction, yes it has the standard 2-1/2" or so by 10" or so oil cooler. The guages are factory fountain, and the sender "looks" to be the original, but don't know for sure. All new filters for fuel, oil, etc....
Can a bad IAC or MAP sensor cause the surging idle and dying?
Does the oil flow out of the engine through the center hole or the side hole on the filter mount, I have a remote filter on the transom. Currently plumbed out of center hole, into "top downriver side" of oil cooler, out of bottom of oil cooler "upriver side" into filter and back to side of engine oil filter mount. This appears to be the way it was plumbed prior to me getting it.................but as we all know that means nothing.

The IAC can cause the surging and poor idle and I do not believe the IAC throws a code.
Your oil temp is WAY too hot.

FROM the remote filter, the oil returns to the motor thru the CENTER port. FROM THE MOTOR the oil leaves the motor thru the outside port...

so its outside to outside , thru the filter, out the filter thru the center, to the cooler, out of the cooler back to the motor to the center.

good oil temp is 200 min to 230 max. anything colder is wrong, anything hotter starts to become an issue to 300 where it starts getting critical.

and your idle issue on the face of it sound like the iac but then again, any pad connection on any sensor will do this as well as having the water temp too cold...

but the iac sounds like the culprit... take it apart, clean it and execise it... make sure it moves and try again.

and obviously vacuum leaks and all sorts of sht will screw you up.

but the bottom line is if you find your oil plumbing is correct, and the oil temp is shown correct, then do not even start that motor again until you discover that cause because having the temp spike with no real load like that is a certain indication of something catastrophically wrong inside. right now you might be able to save it but if you spin the bearing or something actually breaks then you are screwed.

Any chance you changed the dipstick or dipstick tube? Too much oil in pan will make high temps. Usually the pressure will get flaky also. Where exactly is the oil temp sender?

Do you have an IR temp gun you can poke around with?

Ok so I have the oil lines going in the wrong direction. And I put 7qts in the. Engine with everything bone dry. Should I add any for remote oil cooler. I took it to a good merc mechanic friend before the lake test and he said it was 2 qts low an topped it off ( so maybe my dipstick is in a little off and reading low?). So maybe I have been running 2 qts high.
I will change oil lines and remove some oil.... Run again and update.

When trying to find a problem its not a good thing to change two or more items at a time and try and find the problem. It sounds like you have the oil flow direction wrong and you would not be cooling the oil or filtering it properly with that hookup becuase the oil is not going thru the cooler or filter at pressure but bypassing back to pan. That engine has a 6 qt in the pan and 1 qt in the filter, cooler and lines capacity so 7 quarts sounds right. don't reduce the oil to 5 quarts until you get the oil plumbing direction correct and the oil temp in nthe 190-230 degree range unless you see obvious signs of oil foaming on the dipstick. You can always readjust the oil level slightly after verifying dipstick height, system capacity, etc. , get the oil plumbing direction and temps right first.

Yes a bad MAP or IAC acting up can have a big effect on idle quality as well as a manifold vacuum leak. Map bad should show up as a trouble code but not generally the IAC. You can use the squirt bottle full of water and spray the manifold while idling to find a manifold vacuum leak.

Best Regards,
Ray @ Raylar

Thanks for the advise Ray, I had 7 qts in and then the merc mechanic put 2 more in for a total of 9. I probably should suck two back out and remark the dipstick with a known 7 qts in right?

Verify your pan capacity with your Merc model engine but I believe that would be a 6 quart pan. If it is 9 quats would be to much oil but if the dipstick is correct and in correctly that should be pretty easy to confirm.

Best Regards,
Ray @ Raylar

hd,
Before running the engine again, I really think it would be a good idea to pull the oil filter and cut it open to examine it for bearing material. If the oil was circulating backwards, you will need to look in the center of the filter, not the outer layer like normal. If the temp really got up to 310 something is wrong and it might not only be the plumbing direction.

Just my opinion,

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Plumbing was correct, with the exception of going through the filter backwards. Out of engine outside port into filter center port out of filter outside port into top of oil cooler(downriver) out of cooler (raw water side) and back to engine center port.
Is just that and the oil being 2 qts high enough to cause a temp issue?

after the rebuild,the engine's oil pan will hold 7-8 qts and filter ,lines and cooler should hold 1-1.5 qts.

My 502mpi takes 8 qts with an oil and filter change. There is probably another half quart in the cooler and lines that never comes out.
I doubt being overfull is the issue.

What about the lines at the oil filter being reversed?

If the oil level get's high enough so the crank is hitting the oil the temp goes through the roof - On the dyno we used to see about a 15 HP loss for each extra quart. That lost HP = heat. I always check to see where the full mark on the stick is in relation to the windage tray. There is a windage tray, yes?

Where is the temp sender? Is it in the filter adapter? With the routing you have it would be measuring the temp before the cooler.

Me, I always like the sender in the pan. If not there then on the outlet of the cooler, or in the oil galley in the block.

And yes - as Bill says take a look at the filter, that can either be depressing or reassuring.

Just an afterthought, what kind/weight of oil?

If your oil flow thru the filter was restricted to hardly anything (which is what it probably did being plumbed wrong) the factory block bypass valve would most likely open IF you still have one. At this point your motor would be getting un-filtered oil that has also bypassed the cooler. If you tried to drive it like this it WOULD get pretty hot. I would be more worried about getting the plumbing correct and finding out IF motor got hurt than possibly having too much oil. As soon as you run it plumbed correctly you should watch oil pressure closely and be cutting filter open and looking for debris/metal after short time. If you find alot, pull motor out before you destroy alot of parts, Smitty

As articfriends said, that would definately cause a problem and the higher temps.

update:

so tuesday before leaving for Havasu, swapped lines at oil filter (that was the only thing that was plumbed wrong) and checked filter for debris. The filter was clean so I installed a new one. I also pulled my IAC and found it to be rusty and stuck in the closed position. I went out for a quick lake test and immediately noted a HUGE improvement. Oil pressure solid at 60-70 and oil temps never got above 180. Once I ran it a little harder oil got to 200 or so and never any hotter than that.
Thanks to everyone for their engine saving input!!
The idle is still inconsistent though, after running for about 7 hours at havasu, it still wants to die when brought back to idle slowly, and just poking around in the canal, it felt like it could die at any minute, and did more than once. If you bring the idle up to 1000 is very pulsating but eventually evens out and won't die at that rpm level. I changed the map sensor on one day using a friends that was working fine on his boat, but still no change. I looked for manifold leaks with spray test but none are apparent.
Any ideas?
1997 GenVI 502 mpi with vst and mefi1
Only issue is at idle, the boat jumps out of the hole with no hesitation, and pulls very hard all the way to 5000 with no issues at all. The boat ran 67 gps with a 23p hydro Q4

Is your cmi exhaust new? Pressure checked before you put it on? Had the same issues @ idle & now in need of a rebuild because the exhaust was dumping water on a piston!

am glad you coaught this before you killed it. well done.

don't forget to change the oil now that you have some time on it. as for the idle ... it could be a million things but try to think horses and not zebras...

idle is a function of tiny pulse widths at the injectors and small carefully metered amounts of air. if the idle can be maintained correctly static and its smooth then you can make some assumptions from that. it doesn't take much... the fuel and air flows are so small at idle that it doesn't take much to make them " wrong " and turn your idle to sht. and if the idle is shabby and weak then i would go looking for vacuum leaks from a cracked line or something you forgot to put on.

failing that i would have the injectors out and clean them. flow cleaner backwards thru them and pulse them with a scanner until they fan correctly.

on mine i found that a couple of things were common... first that they get rusty and dirty pretty easy and the fan gets shabby and the other is that it takes nothing at all to clog the screens.

a good spray pattern is really crucial to making an injection system work properly. for me it was a simple matter of taking a pump and a can of very aggressive cleaner and with a hose and a clamp pumping fuel to the injector from both directions while pulsing it with a scanner. you could see the pattern clean up immediatly and the junk that would come out of the screens was significant.

i suggest this to you because your boat has been sitting around while the motor was being done so the tank has some junk in it and the lines might...

you have two things to remember ... first that you have had everything apart there is to have... so touch and rub all that stuff again... and second, things like filters and old fuel and all manner of forgotten stuff will consire against you from the boat sitting... make sure all that is correct first... and have another look at the iac and make sure ir moves smoothly and that the seat and port are clean. and if you don't have a scanner , buy one. it is a crucial piece of equipment for you. i have one if you need it

horses... not zebras

Have you checked the timing????? It should be set at 8* when put into base timing mode.

Short question to the experts.

MEFI 1 502EFI 1993.

Diacom read over 3100RPM to WOT only 29,53 Spark advance.
Base time are set so 8°.
EFI dont make 34° at WOT is it nomal?

Thank you.

well... a few things...

first you have to look at which ecu you have and what the total timing is supposed to be in that unit .

second, make sure that no one has " reflashed it" and changed whatever they could have changed.

third, check the diacom numbers with a proper jumper and timing light just to make sure you are actually interpreting your diacom data properly ... i useded the much much older diacom systems on oldsmobile motors and the data was often "raw" and did not actually answer the quetion you thought you were asking...

and fourth... i suppose you could have something triggering the knock sensor and backing the timing off...

Hello stevesxm,

thank you for the info.

I have the first MEFI 9550 two ECM´s and two ECM´s reprogramed.

If i drive with 2500 RPM i see in diacom 37° and with the timing light i go with -37° to 0° with the light. At WOT diacom shows me 29,53°, but i have not read it with the light.

Now what make me confused. I have Base Time 5° for test.
Diacom Show 37° and timing light shows 37°, but not 34° at 0 ore 37° at -3°. Where are the 3°.

I have test base Time 0° and 10° all the same. I have no Crankposition sensor.


All other people have say to me. Diacom shows only the Table and i have to add the 8°.

Diacom 29 + 8 = 37 ???

ore is it

Diacom 29 = 29 real with base 8
Diacom 29 = 31 real with base 10
Diacom 29 = 33 real with base 12
???????????????

I have no Table from the ECM 9550 so i can not say what the timing shout do at 4860 RPM.

"and fourth... i suppose you could have something triggering the knock sensor and backing the timing off... "

Can the flappers in the Imco Endtips can do this ??

i'm sorry but i simply don't know. i understand what you are saying and i understand your confusion but wiythout seeing the screen and the understanding the current diacom data, i would just be guessing in an area where it is not smart to do so. i think if i am standing where you are i am going to just make absolutely certain that i understand the timing marks i am looking at and i would use a very simple timing light... one without the advance dial... and make sure i wasn't running 37 degrees or anything like that...

beyond that you need someone genuinely familiar with whatever version of the software that diacom is running now. and i apologize but thats not me. have you tried contacting diacom ? when i was using their stuff you could just call them and talk to them...

OK good idea, i ask Rinda. What the Spark Advance Show me.

I can use the timing light with 0 like a light without the advance.

I see in Base time 8° with light at 0°
I see in Base time 0° with light at 8°

I see in Rinda 29,53 at 3100RPM with timing light 29 i see at 0° the light.

I ask Rinda.

[QUOTE=MikeScarab28XLT;3679117]OK good idea, i ask Rinda. What the Spark Advance Show me.

I can use the timing light with 0 like a light without the advance.

I see in Base time 8° with light at 0°
I see in Base time 0° with light at 8°

I see in Rinda 29,53 at 3100RPM with timing light 29 i see at 0° the light.

I ask Rinda.[/QUOT

they are or were a very good company. when i
" knew " them they were actually making all the oem test equipment for GM ... a GM factory scanner was actually a rinda designed and manufactured piece... so they aren't some aftermarket outfit... they have been around for very long time and have ( or at least used to have ) the inside track at GM ... so i would start there.

but first just make sure you don't have TOO much timing in the thing and do some harm before you get your answer.

I have ask Rinda:
if i drive what shows me the program? The programed table ore the table +8* base time.

If i see 29,53* in diacom at 3200 rpm.

Are the 8* base includet ore not.

What total i have if i see 29,53* in diacom?

29,53 + 8 = 37,53 to high
29,53 - 8 = 21,53. To low

anwser:
You would have to ask MerCruiser, we simply display the timing data that the ECM reports to us.

MerCruiser sets up all of the ECM data tables and software.

We don't have any engines here, we are software developers strictly working on the diagnostic tools.



cut the case down

I do not trust the timing lights that are supposed to measure the advance. After testing every one on the S*** - *N truck with my distributor machine could we not find one that did not have at least 3 deg error. I will admit this was a long time ago and they might be better today. I do not trust them even when set to 0.

Nothing beats a degreed balancer.

The ECU and the data shown on your scan tool have no idea what the base timing is. As you know there is no crank position sensor like on the new engines. So yes - the total timing is going to be the reading shown + the base.

If not locked in base timing mode it will move all over the place and 30 degrees (plus whatever the base is) at part throttle with some vacuum in the manifold would not surprise me at all.

If you have an 8" balancer it is easy to put a 36 degree mark on it, that works out to be 2.513 inches. Which makes 2.5 inches just a fraction off. Use a flexible machinists scale and put a mark at 2.5 inches to the right of your 0 mark. At least you will have a reference you can count on. And coincidently that is where all the stuff we used to build liked to run at.

You did check your TDC mark and pointer to make sure it's TDC, yes?

Thank you Mbam for your help.



I have changed the MArkV Block to MarkVi and now i have a Timing gain cover with only one pin. Hope it is 0 and the old balancer.

i have rotate all Spark plug wires on the distributor Cap, becouse i had no room to rotate the distributor (oelcooler, Ram, VST,)
Is it important that the marking 1 on the distributor cap are the wire 1 ? Ore can i rotate all spark plug wires 1 pin.



If i put a marker on the balancer with the making 32*,can i rotate the distributor at 4000 RPM and timing light at 0 advance that the light point to the 32* marking. Than i can double check it with 32* advance on the timing light and the light point to 0* on the balancer.

I have buy 2x tapes from Mr. Gasket #1591. Chevy 8" Dia.

I go testing.

Yes, you can move the wires anyplace you want. My preference is to keep them in agreement with the numbers on the cap, makes life easier down the road. Pull the distributor and move it a tooth.

I would allso get a pison stop, the kind that goes in the spark plug hole. Pull all the plugs and check TDC. I can't remember if the valves will hit the stop, best to pull the rockers unless someone here knows for sure. You should be able to find instructions online someplace how to use the stop. I am too poor a typist to do it here !

My new cap have no marks, numbers on it.
OK tape flay away in some seconds. I used the tape to mark the balancer with a white pen.

Now i have make a base time to 10*.

Now i have test it and the diacom sows me 30* not the 29* last i have see???????
But it shows me 30 including the base of 8. Real light i have the 32* on the markings. So i have to add +2 to rinda. 8+2.

If rinda show me 30 i have 32 real total. 28 with rinda i have real 30 total. Now im more happy to now it.

http://www.offshoreonly.de/phpbb/dow...0816&mode=view

http://www.offshoreonly.de/phpbb/dow...0817&mode=view


this is not running engine
http://www.offshoreonly.de/phpbb/dow...0819&mode=view

deleted

since this thread seems to have gotten hijacked, I need some help on the original topic of my surging idle and wanting to die.

Just ran the boat on the hose, put a fuel pressure guage on it and found something interesting..... I also checked the manifold for any leaks by spraying carb cleaner at all gasket areas and no leaks were found. My static and running fuel pressure are at 30psi. when I bump the throttle to 1000 or 1200 and get my surging, the fuel pressure also surges from 30psi down to about 27 psi in sync with the pulsing of the engine.
This is a VST 502 all stock except for cmi etops. Have already replaced IAC, checked MAP sensor, and no changes. this seems like perhaps a fuel pump issue???????
Also code scanned and no codes found.

Hello high&Dry,

i have the 1993 engine, the only i have read are allways 37-39 PSI on FuelRail. I have buy some new Pressureregulators original from Mercruiser and the make allways 32PSI without vaccum, with are 27PSI. The pusling i have too. I have than canches bots mechanical Fuel Pumps, same pulsing in fuel pressure.

I have test adustabel fuel Pressure regulator. I put the fuel pressure to 39 PSI, 40PSI and 45 PSI no diffrence. At 45PSI the boat are slower, so much fuel :-)

I have buy the EFI Upgreat Kit with ECM reprogramm and the have say to me go from 39PSI to 45PSI. But the engines not run. I go to 32PSI and the new programm works. But slower than may stock ECMs. Im happy becouse i have 4 ECMs. 2 Original and 2 reprogrammed.