Help! 88 Coupe ..Hard start when hot ?

[mrroadhouse]

My 88 Coupe starts instantly and runs well/and normal (with exception of occational check engine light that goes out for 6 months at a time ) when COLD. Problem is that after warm up it take several seconds of cranking to restart ( 5 min or 5 hrs no difference). Let it sit over night and instantly starts again.

 

[Schrade]

edit:
Always check codes first, as "Hib" suggests in the next post. It should be stored in the computer as a 'History' code (that is, if early c4 keeps codes as 'history').


Leaking injectors - like having the choke on when it's warm - it floods out.

Confirm by doing fuel pressure leakdown. Takes 10 minutes, if you take your time.

 

[Hib Halverson]

My 88 Coupe starts instantly and runs well/and normal (with exception of occational check engine light that goes out for 6 months at a time ) when COLD. Problem is that after warm up it take several seconds of cranking to restart ( 5 min or 5 hrs no difference). Let it sit over night and instantly starts again.

What code is set in the ECM?

Also, take "Schrade's" advice on testing fuel pressure. Good chance you have leaking injectors.

 

[chuck121566]

In addition to the injectors, you may also want to check your fuel pressure regulator. The diaphram in mine was shot and caused similar symptoms.

 

[Schrade]

In addition to the injectors, you may also want to check your fuel pressure regulator. The diaphram in mine was shot and caused similar symptoms.

Yes - another good point... and perhaps a little explanation is in order, if he doesn't exactly know what to look for.

There's a vacuum supply TO the FPR, FROM the intake [source]. Changes in vacuum determine enrichment, or en-'lean'-ment.

The diaphragm has vacuum on one side, fuel on the other. If the diaphragm in the FPR is letting any gas through the bladder, TO the vacuum, it dribbles into the intake by the vacuum - again, like having the choke on a warm motor (see#1).

Find a diaphragm hole by pulling the vacuum from the FPR, COLD motor, with JUST the fuel rails primed key turned 'ON' motor off. STRONG fuel smell in the hose means bladder needs butter. If you're not sure, feel for fuel around the vacuum port on the FPR.

Some FPRs also have a spring which wears out, which could also allow the fuel to dribble out of the injectors (and a hard hot restart), but that won't show until a FP test...

But again, check codes FIRST, like "Hib" suggested #2.

 

[boomdriver]

My 88 Coupe starts instantly and runs well/and normal (with exception of occational check engine light that goes out for 6 months at a time ) when COLD. Problem is that after warm up it take several seconds of cranking to restart ( 5 min or 5 hrs no difference). Let it sit over night and instantly starts again.

Fuel pressure/filter symptom.

Also the fuel regulator can wear internally and allow pressure to escape to the return, not necessarily a leak to the vac side. Having this problem will often show sufficient pressure to the gauge, but much of that pressure is dumped back to the return side instead of going to the injectors. Lean fuel, lack of fuel at the inj is the result.

Hard restart, or hard to start hot often means a lack of fuel. Too much fuel is evidenced by the smell of raw gas.

 

[vetteoz]

Problem is that after warm up it take several seconds of cranking to restart ( 5 min or 5 hrs no difference). Let it sit over night and instantly starts again.

Try a hot start with your foot on the pedal.
If it starts " easier" you know you have a rich cond from fuel leaking into the intake from somewhere.
Opening the throttle allows extra air in to dilute the over rich mixture and stops the injectors spraying fuel in
When car sits overnight , the fuel evaporates from the intake so you get a normal start when cold

 

[mrroadhouse]

thanks

Thank you all for the suggestions and guidance I will research with this new information !