Engine is hard to start when hot. Have changed out fuel filter, fuel regulator, spark plugs, and it is better but still hard to start when hot. It was hard to start when cold but has improved with these changes. Approx 105k on milage. 4 cy

hot soak ,no starts 101:
which engine?, cant guess that. say it. please."name /size"
is it flooding or starving
hard to start , so that is easy you are parked, and makes diagnosis so easy, (no need to move)
you skipped the fuel filter:?
why not use a scan tool now.?
you crank for 5 seconds, see P03xx errors. DTC'
THE ECU REPORTS ALL CMP AND CKP SENSOR ERRORS!
bingo now you have your answer , finding this, scan tool free is hard hard work. am i to tell you that hard way, sure.
1:test spark on all cylinders ,same way 100 years, google it.
2: ok sparks good, i check all spark plug tips, for wet and dry or soaked in fuel.
3: i see dry, , i use test fuel (same way for 100 years,)
run on test fuel (my Model a ford, same way works.....)
4:; ah one plug is soaking , ah leaking injector
5:ah, all plugs wet, (too high fuel pressure, ECT stuck cold
if all are wet, I stop, there are lots of tests for this.(bulleted below)

• fuel pressure (KEYON, cranking and running and W.O.T.)
• injector leak down tests. all of em;'
• injector balance test (ALL)
• Fuelpump regulator 4 tests

all this perplexing, get your ASE mechanic in the loop.

The check engine will be on if the key is on but engine not running . This is normal. If the check engine goes out when the engine starts there are no codes present . Did you check the fuel filter . Sometimes when a filter is dirty there is sedement laying in the filter canister . When the pump starts working the flow picks up the sedement and plugs any remaining open screen and stops the fuel completely . The engine stops . When the flow stops the sedement falls back allowing flow again. and the engine will run for another while . If the filter is old it should be changed anyway . Also when the engine stops check to see if there is spark at the spark plugs while cranking the engine .

hi martin i am shannon . you will first need to determan if the problem is fuel or spark related . for fuel just add 1 oz of gas into the intake through the throttle. you will need to remove the big black hose at the throttle . just pour the fuel in. if it starts right up then you have a fuel issue most likely a bad fuel pressure regulator. too test the spark i would get a spark tester . connect it to one of the plug or coil wires. set it to 25.0000 volts then have some one turn the engine over while you which for spark. if you get no spark you may have a bad crank angle sensor. hear is a spark tester i use . this one is at Autozone.

this is most likely a fuel vapor issue.

fuel boils in the fuel rail causing a hard start after a 'hot soak'.

the fix is to replace the fuel pressure regulator and the pcm. good- day !!

Hi Mark. I was thinking the same type of problem. Either the fuel pressure regulator, a fuel leak or the fuel pump.

you better to change fuel filter and make service ,i.e. to change spark plugs, air filter .

Being an older car, unvariably, it's best in my opinion to start cheap, without rebuilding the car. Check spark plugs, and/or replace. Check or replace spark plug wires next . assuming your engine lights aren't coming on when it is running, if they are, it could be faulty emissions system components or a vacuum leak in the fuel injection system, intake manifold or hoses. Check your fuel pressure regulator and/or replace. It could even need ignition coil and module replacement. Lastly, the fuel pump could be faulting... On an older vehicle such as this one, it's better to understand what kind of maintenance it has undergone. Good luck and start cheap!

air filter really dirty, injectors stuck open. fuel pressure regulator is bad.

check fuel pressure, check fuel pressure regulator, change fuel filter. If fuel pressure is low it could be a bad pump, a clogged filter, or a malfunctioning fuel pressure regulator. If all those check out, then check crankshaft and camshaft position sensors.

that has a votec engine in it the fuel pressure is droping at knight and it takes 60 psi before the injectors will fire most likely cause fuel pump ,leaking injector ,or a feul pressure regulator