Jump to content

Welcome to TheMalibuCrew!

As a guest, you are welcome to poke around and view the majority of the content that we have to offer, but in order to post, search, contact members, and get full use out of the website you will need to Register for an Account. It's free and it's easy, so don't hesitate to join the TheMalibuCrew Family today!

Hard starting - Sputtering Popping

Recommended Posts

New owner of used 2002 Malibu Response LX, have gotten tons of useful info already off this forum.  So, mid-trouble shooting, thought I'd both share a few things I've learned and also reach out to bright minds that might have other ideas for me.

Boat runs great between 2k-5k rpms.  But, if warmed up and left to sit awhile, either won't start at all (cranks but tries to catch but never quite fires up) or fires up to a very rough sputtering idle where the only way to get back to normal ops is to flutter the throttle up and down between 500 and 1,500 for several minutes.  During that time there's sputtering and popping then suddenly it will come to life as if nothing happened and run perfect.

Have already replace plugs, plug wires, rotor and cap.  Then decided must be fuel so fuel filters and cleaned fuel pump intake screen.

Fuel pressure gauge shows 45 at key turn, then holds 42 at idle and under load (though during starting flutters between 30 and 40).

Thinking fuel was bad or fuel filter was clogged, all fuel replaced, then tried pouring small amounts into throttle body when it wouldn't start to see impact.  No change.  Still wouldn't start.  Checked coil spark (good), then spark plug spark (good).

Finally decided it must be too MUCH fuel because unplugged fuel hose and after a few seconds it fired up.  Then if reconnected it ran great.  Until it warmed up and left to sit awhile, back to no start.  So I did WOT on start for a flood clearing, and it will then start but run rough a few minutes then run good again.

Just had fuel injectors inspected.  One had deformed o-ring and probably was letting in clean air (likely source of sputtering/popping backfires).  All had some leakdown (likely source of hard starting, but not so much leakdown to explain flooding that leads to a no-start).

Cracked PCV found, soon to be replaced, but while maybe a problem also not likely to lead to a no-start.  So I've got fuel (too much, apparently) and spark.  But often no running engine.  Soon will be putting back in fuel injectors with new seals and replacing fuel regulator and PCV.  Likeliest culprit seems to be fuel regulator letting fuel through into throttle body.

Now the tips:  couldn't find PCV or fuel regulator anywhere in parts catalogs for local marine stores or parts stores.  Turns out Cadillac 1996 4.6L is a perfect match for both of those.

I'll need replacement fuel injectors to fix the leakdown but can't find them anywhere.  For now, existing will work but their dripping leak down will only get worse and they'll need replacing too.



Link to comment

Classic vapor lock - have the same boat and ran into the same issue. This ethanol based gas along with the “winter” blend inventory extending further into the summer due to the dramatic demand drop (COVID) has exacerbated the issue this year. Look into adding the low pressure Carter fuel pump just after the tank in the ski locker. Our boats have the fuel pump on the side of the engine which makes it prone to heat soak.  Later models have moved it to inside the fuel tank for this very reason.  In the meantime, to get you on the water quicker you can pour cold water on the fuel pump - works every time....  Also, I’ve found that using quality premium fuel from name brand stations has helped. Search vapor lock - many threads on it here.  

Edited by Gary Pelletier
  • Like 2
Link to comment

Thank you both for the tips I hadn't considered that. Fuel injector guru said I can still use injectors because leak down wasn't too bad, but that they'd ultimately need replacing. Fuel regulator leaking fuel through the vacuum line into the air intake was his idea. 

Put injectors back in with new pcv valve tonight and tested it. Started up fine, still solid correct fuel pressure. 

Pulled the regulator vacuum hose off and was sad to see it was totally dry. Tomorrow I'll run it under load up to full temp just to confirm nothing is wrong with the regulator. 

The things that makes me hesitant about concluding vapor are 1, it's not even been very warm any of the days I drove it (like 78 at highest), 2 in a couple cases it still wouldn't start even after engine had definitely cooled off (engine temp under 100), and 3, vapor lock doesn't seem to explain why the occasional rough idle with sputtering and popping. Or does it? I've never had a vehicle with the dreaded "vapor lock" so i guess to me it's always felt like that was often a white whale kind of nearly mythical mystery diagnosis. 

Does any of that make you think differently? Or do those symptoms still point you to the vapor lock diagnosis?   If yes, anyone got a part number for the recommended Carter pump? What's low pressure, like 20 psi?

Link to comment
11 hours ago, MCAHunter said:

If yes, anyone got a part number for the recommended Carter pump? What's low pressure, like 20 psi?

I say again, 5th paragraph in the posted link above.

Edited by formulaben
Link to comment

For the good of the crew,  I've got the answer, and it's not vapor lock. Replacing fuel injector O rings and replacing the one electrical connector to one fuel injector (the loose one) was the trick. 

Starts and runs fine, smooth, etc. Still a little slow starting when hot, but that makes sense knowing the injectors still have a decent amount of leakdown internally. I'll find replacements this fall after the warm weather passes.

Thanks again to those offering help. 

  • Like 2
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...