won't start when warm

[liz]

I have a 1993 q45 and for some reason it starts good when the engine is cold but once the engine warms up it is difficult to start. the mass air flow was changed, the fuel pressure was checked and was fine, and so was the fuel pump.. Do you know of any other thing that can cause this?? the car is also slugish compared to what it was before the problem startedThanks

[Kiven422]

To me it sounds like your fuel pump is about to go. My 93 Q was also very sluggish and hesitated badly if you were even slightly harder on the gas (big rigs could accel/climb faster). It would start 97% of the time but after 2 hour drives it would not start until the car cooled down.

The fuel pump is a problem that from my knowledge happens on nearly EVERY Q45 (its been replaced on both of my Q45's). If your over 120K miles this can be expected...

If this is not your problem I'm sorry I have no idea then but if it sounds like your problem you will need to get a new fuel pump and fuel pump control unit. Try and avoid the used stuff if you can.... don't want another pump/FCPU to go bad.

[96Qowner]

Find your FPCU under the rear deck and jump it to ground the next time the car won't start. Here's a thread on the subject with pics and diagrams:

How to bypass the Q45 FPCU - Fuel Pump Control Unit

[maxnix]

And what were the "fine" fuel pressures?

Have you read the timing chain guide article? Very important that you do so!

[elwesso]

Yeah I'd like to see a number for fuel pressure.

[liz]

The feul pressure reading is 37-42

[maxnix]

That should work. Measured after the fuel filter? When was it last replaced? Had any injectors out lately?

[liz]

I haven't replaced the feul filter

All this started after the car was rebuit because it had a blown head gasket

[Q451990]

All this started after the car was rebuit because it had a blown head gasket

There's a useful tidbit of information! What caused the head gasket failure? They are very rare on the Q45. Massive overheat? Or was it leaking hoses under the plenum that had someone confused into thinking it was the head gasket? Who did the work - someone with Infiniti (or at least Nissan) experience?

Heath

[Q45tech]

Never seen good luck with any blown head gasket engines which result from owner abusive overheats.

Too many thing exposed to abnormal heat are accidents waiting to fail not to mention the aluminum warpage affecting cams and heads, bearings.

What evil person talked you into a partial low quality rebuild?

Why did you wait to tells us that the problem started after build?

[liz]

yes massive overheat

[96Qowner]

That's bad news, liz.

But one thing to check - trace the cables from the battery to the starter. Another member had similar trouble and found a bad positive battery cable assembly.

zerothread/302079

Eventually needed a starter.

[maxnix]

yes massive overheat

Oh oh. Much better to install an inspected and rehabilitated JDM take out.

Did they check the heads for warpage? What caused the overheat. There may have been more than just head damage.

Has your shop ohmed the injectors through the harness?

Surely at a minimum they replaced the cooked knock sensors and harness?

[liz]

what is JDM?

the heads were not warped & i ran it hot

[Q451990]

JDM = Japanese Domestic Market. Essentially we're saying that it would have been better to have swapped the whole engine with one that was taken out of a car in Japan and shipped here.

How do you know the heads weren't warped? What all was done during the repair? We really need a detailed history of what happened, and what was done to fix it. My guess is that you either have compression issues due to the overheat, or more likely a flooding condition due to something with the fuel injectors. Does the stater work, but the car just cranks and cranks for a while before starting - or does the starter work? If you could have someone watch the exhaust pipe after the hard start and tell us if you see dark smoke that would help too.

Heath