525EFI Warm start problem - ??
 

Recently replaced the long block on one of my 525's. The motor runs great but I'm having a pesky problem with warm starting. When the engine is cold, it fires right up. When the engine's been idling for 10-15 minutes and is restarted, it fires right up. When the engine has been run for 45-60 minutes and then immediately restarted, it fires right up. However, when the engine has been run for that same amount of time, then sits for an hour or two (as in a stop for lunch); that's when the problem kicks in; the engine has cooled down somewhat, but it's still warm. It takes at least 3-4 turns of the key to get it to turn over. Pushing the throttle forward a bit seems to help it along but I shouldn't have to do that. Every other starting scenario, the engine lights up as soon as I turn the key. I've already replaced the IAC, the crank position sensor and the cam sensor and pressure tested the headers.

Any other ideas?

Almost sounds like a vapor lock issue. Next time you stop for lunch or something leave the hatch fully open so the heat doesn't stay in the engine compartment and note if the problem changes at all.

I leave my hatches open every time after running to let things cool off. Makes no difference for this problem.

Maybe use a Rinda to scan before and after the problem to pinpoint? I am looking to buy one to keep an eye on everything.

In my book, turn over means turn over ie: crank over.

Running means running.

So, just to make sure, as others are assuming you mean running, is it not cranking or not running until 3-4 turns of the key.

It is not running until 3-4 turns of the key. That is, the engine will crank normally but not start running until 3-4 turns of the key. With each successive turn of the key it seems to get better, ie: first turn of the key, the engine cranks but nothing happens. 2nd turn, you can hear a few cylinders fire as I start to hear exhaust noise but doesn't quite fire up, 3rd or 4th, she starts running. If I turn off right after the start and try to restart again, the engine will fire right up... bizarre..

your also cycling the fuel pump at the same time, maybe the system is losing pressure over a period of time and not holding adequate rail pressure

Good point. Mechanical fuel pump starting to go?

u have a fuel presure gauge on the dash?

Hmm.. interesting but I just replaced all three mechanical fuel pumps two months ago..

I do not.

try cycling switch without turning motor over and see if there is a change . i think you are on the right track with the fuel pump

I replaced both of my mechanical pumps last year for maintenance, original with wasted oil in them. Ran fine for 1 hr then 1 engine started to lug and was really hard to start and keep running. Then it wouldn't start at all. Turns out my brand new Merc mechanical fuel pump had almost zero pressure when tested after we got back in. Installed another brand new one and problem fixed.

@HyFive578: sounds like it could be a "hot soak flood" condition. This is caused when the fuel pressure is fine but some or all of the fuel injectors are just dirty enough to let fuel seep into the cylinders when sitting for a while (say 20-60 minutes) with fuel pressure, causing a flood condition. The flood condition is of course cleared with extended cranking.

Had this on an 87 Corvette MPI engine, and it was cured by GM replacing the (presumably) faulty injectors under warranty. However, it can also be caused by fuel contaminants leaving residue on your injectors so that they don't close and seal perfectly. A good fuel injector cleaning procedure may cure things. IIRC this can be a pressurized can of cleaner that you attach to the Schraeder valve on the fuel rails while cranking.

The old engine ran and started fine with the new fuel pump. The problem didn't start until the engine was re-assembled with the new long block.

I think you may be on to something here. The need to crank the engine over and over again before it starts reminds me of a flooded engine. When the engine was torn down, my shop sent the injectors out to be serviced. I wonder if they were maybe damaged in that process or when they were re-installed in the rail. Pushing the throttle forward a little when cranking the engine helps it to start; any significance to that?

This problem is intermittent, so taking off the intake and checking the injectors every time this happens really isn't practical, is there something I can check right at the time when the engine fails to start to see if this is the issue?

I can't promise this will work, but a trick I used on EFI engines that I suspected were loading the motors is to pull the air intake tubing, open the throttle blade all the way and take a good long sniff. If I smelled raw fuel than I had a good idea my fuel pressure bleed off was going into the motor. Perhaps pulling the flame arrestor and taking a sniff might lead you somewhere? I would also measure fuel pressure and see how long it takes to bleed down after shutting the motor down compared to the other two motors.

Absolutely, pushing the throttles open would be allowing more air into the engine to help lean out the overly rich condition.

Think of holding a carbd engine gas pedal down half way or more when its flooded to get it to start.

Time to check fuel pressure and see how fast/slow it bleeds off compared to one of the good engines.

Thank you guys!! How do I check the fuel pressure?

There is a test valve on the fuel rail under the intake plenum. Looks almost like a valve stem on a tire. I have to double check but I think 41-43 psi at idle is the spec.

Thanks guys!! I think you guys are on the right track with the fuel delivery system. Going to start there..

It absolutely does. Beyond opening the TB blades and allowing more air in readings from the TPS cause the ECM to go into flood clear mode which shuts off the injector drivers so no more fuel is added.

wybmabilty hit it spot on with hot soak flood condition. I've had this happen as well thinking it was vapor lock. It is NOT vapor lock. Motor is flooded pure and simple. How it happens depends. The injector issues addressed are one possibility. Depending on the fuel system, pump configuration and plumbing there are some times vent lines that vent vapors into the manifold causing the same condition. I know this happens on VST equipped motors and is often mistaken for vapor lock.

Makes complete sense to me. The engine behaves like its flooded. You guys are probably right. Going to check the fuel pressure this weekend and see where that leads. I'm suspicious of the injectors. They were sent out to be repaired when the engine was being reassembled. Thanks!!

I have zero personal experience here, but have read a few threads where when the injectors are sent out for tuning/cleaning they come back a little sticky from the detergents they use. That seems wonky to me, but there you go.

It's true. Have gone thru many vendors over the years where I've had sticking injector issues.

Those that didn't, won't tell me what they use. Damn it. Makes it hard to find other vendors that will have issues or not.

BTW: we all know gasoline is flammable, therefore injectors won't typically be sent with fuel in them, thus why other fluids.

Put a new short block in one of my engines last year swapped all necessary parts
525 efi motors also ..in the heat exchanger there is a temp sender somehow in between pulling the old motor and rigging the new motor it went bad .. I could start the motor cold and if I let it run any more than 10 min it would not restart again unless I waited an hr or so .. If I held throttle wide open( clear flood mode ) it would restart after a lot of cranking .. Turns out temp sensor was the only issue .. Motor simply thought it was cold and dumps more fuel even when warm ..they have a new design temp switch .. Early ones were all plastic the replacement is brass. ..u have to remove heat exchanger to get at it

I can start the motor at any time, it just takes a lot of cranking to get it to fire after its been running and sitting for a while. If I run and then immediately try to restart, it fires right up. The only time I have the problem is when it's been run and then sitting for an extended period of time, like an hour or more.

yes the same with mine I could start it anytime but a lot of cranking also .however when cold fires right off

Are you referring to #36 in this diagram? If so, wouldn't SmartCraft detect that the sensor was bad?

[ATTACH=CONFIG]530194[/ATTACH]

http://www.mercruiserparts.com/Show_...tem+Components

I had the same problem with the engine yesterday... cold start fired right up... ran her for 15 minutes, let sit for 2 hours and it took me 4 turns of the key to get her to fire.. I hooked up a fuel pressure tester yesterday to test the leaky injector theory. Got around 40 psi at idle and it took over 2 hours for the pressure to bleed down to around 16 psi and then I let the pressure out manually. I would think that if the injectors were leaking, the pressure would bleed off much faster than that. I think I will try to replace the temp sensor on the chance that Smokin Gun's theory is right, but any other ideas?

Did not read all the post up here. Here is what I think your problem could be.

1. Coolant temp sensor
2. MAP sensor out of spec range
3. Electric fuel pump - internal check valve problem

I would have thrown IAC in the mix but I seen where you said it was changed. I would scan the motor and look at the ranges of the sensors especially the 3 listed here.

Next fuel injector cleaning & testing. I do not have a the biggest name on the block for doing this type of service, but I have posted some really good info before about what to look for. I have been doing fuel injector flow testing - cleaning services now for over 5 years with a custom professional machine - NOT what you see on youtube - good luck with that.

First thing is any or all basket filters are removed from the injector that is the first step, then the injectors are flow tested to see the results from many test specs like flow rates, flow patterns, leaking, ohms test and so on. Next they are put into a an ultra sonic bath that cleans them up fairly well, some great and some not the best (injectors).

Next the injectors are flow tested again to compare the results from the first time around of flow testing. The flow testing solution is not fuel - mine is a match solution with the same specific gravity of fuel - why because you want it to flow like fuel. Next is, I have a back flush unit that when you turn the injector around, put it in the unit, it will back flush all the bigger particles that could not pass thru the very tiny pintles when cleaning in the ultra sonic bath. Next is after back flushing there is no more flow testing or cleaning solution in the injectors.

Also if the company does not have the back flush unit (many do not especially anyone with ASNU machine) you still turn the injector upside down inwhich dumps most of the flow testing solution fluid out anyways. No one that I know - who does this type of service, ships injectors with cleaning fluid solution in them because your last step is flow testing them, then turn them upside down to drain as much of the solution out. Anyways the very short short story about it. I clean many marine industry businesses fuel injectors from Yamaha to Volvo to Merc to Mercruisers to Johnson / Evenrude for over 5 years now.

Thanks BUP. I will investigate those suggestions. Unfortunately, I winterized yesterday so this is going to have to wait until the spring to get resolved but I will make a note of these now.. thanks!

Had a internal check valve fail on a fuel pump on a 2005 525 that caused us to pull our hair out checking things over. Good luck in you search for the cure.

cycle your keys,,no cranking,,,3-4 times,,,allow 3 seconds between cycles,,,if your bleeding down to 16psi,,,this will get you back to 38-42psi,,which is what youll need for it to fire-up,,,now you can either live with it,or start going thru your cool-fuel system,ie high pressure fuel pump.

Hmm... that's interesting.. it took over two hours to bleed down to 16 psi.. are you saying that it should hold 40 psi for longer? What is the normal rate of bleed down?

16 psi is low,,,yes it should hold longer than two hours,,,check one of your other engines for reference,,,if you can still get to it,,you can use a fuel gage to check this problem,while its laid up for winter

I winterized the engines on Friday. I will have to retest in the spring..

thinking about this some more... kinda doesn't make sense because the engine will fire right up when cold and presumably the pressure has been bled down if the boat's been sitting for a week or two...

Now that its spring and I had my first run this past Sunday, I'm reviving this thread from the end of last season as the problem is still there.

Here's the problem:

The motor has a hard time starting when it's been run, sits for an hour or so and then is restarted. When the engine is cold, it fires right up. When the engine's been idling for 10-15 minutes and is restarted, it fires right up. When the engine has been run for 45-60 minutes and then immediately restarted, it fires right up. However, when the engine has been run for that same amount of time, then sits for an hour or two (as in a stop for lunch) and then is restarted, it will crank and crank, but will not start. I can get it to turn over by rocking the throttle and coaxing it somewhat, but it takes a lot of cranking to do that.

Here's what I've already done.

- replaced the IAC
- replaced crank position sensor
- replaced cam sensor
- serviced all 8 fuel injectors and had them flow tested
- replaced fuel regulator
- checked fuel pressure and bleed down after running, (takes about 2 1/2 hours to bleed down from 42 psi to 16 psi)
- checked fuel cooler for blockages
- verified insulation jackets covering all fuel lines going into the fuel cooler

I haven't tried cycling the key 3-4 times before restarting to see if that makes a difference, that's next. Possibly going to take apart the fuel cooler assembly but I'm not sure what I'd even be looking for in there.

Any other ideas people???

I would replace the high pressure pump, I understand the system is holding pressure but that doesn't mean its working correctly all the time, how many hrs are on the pump ? which engine is it


I've got 6 pumps if you want to try one