: cant fix hard hot start for the life of me



fpmesiIII
06-04-07, 10:19 PM
I have tried everything. new FPR, new fuel injectors, cleaned throttle body. anyone know what causes a hard hot start? i will go through and check all that apply.

Ranger
06-04-07, 10:34 PM
Hard hot stars are usually the FPR or leaky injectors. How about the fuel pump relay?

fpmesiIII
06-04-07, 10:49 PM
well i replaced the FPR not too long ago with a brand new one hoping to fix the problem. but it didnt. then i started getting into the injectors. i purchased a new set off ebay. hoping that it would fix the problem. but has same problem as before. i havent checked the fuel pump relay, how do you do that?

fpmesiIII
06-04-07, 11:40 PM
also the car when driving also has a jolt when you give it some gas. its like a hesitation then a little powerful jolt for a second. as you keep your foot depressed on the gas pedal it smooths out. but whenever you take off and put it back on it happens again.

Ranger
06-05-07, 11:05 AM
Try tapping on the relay with the handle of a screwdriver. If that does not help, swap it with a known good one to see if it does the trick. If not, then that is not your problem.

fpmesiIII
06-05-07, 12:05 PM
well i went out and tapped the relay with the head of screw driver. it seems to have helped with the gas jolt. it didnt go away completely but it seems to have lessen the occurance of it.

what exactly does tapping the fuel relay do? should I just replace the fuel pump relay? my father has a 96 deville that runs perfect, i will take his out and see if it fixes the problem. its gonna be a shame that i spent all this money on fuel injectors and it turned out just to be a fuel pump relay. but hey atleast i learned to perfection how to replace injectors. i can probably set a record for changing them the fastest.

there seems to be a piece of black electrical tape wrapped around both the fuel pump relay and AC relay. could someone in the past have tried to fix the problem with this piece of electrical tape?

EcSTSatic
06-05-07, 12:06 PM
Tps?

fpmesiIII
06-05-07, 12:11 PM
i will try replacing this fuel pump relay. then im assuming tps is (throttle position sensor?). where is that located and how do you check it?

Ranger
06-05-07, 05:08 PM
Tape on the relays is likely from the factory. Tapping it may jar the contacts loose if they are stuck open. The relay comes into play during cranking only, so it has nothing to do with your "jolt".

fpmesiIII
06-05-07, 08:16 PM
Tape on the relays is likely from the factory. Tapping it may jar the contacts loose if they are stuck open. The relay comes into play during cranking only, so it has nothing to do with your "jolt".

right ok i see. i have noticed today that it hasnt hard started since tapping on it. but yeah it still has the jolt. any ideas how to fix this problem?

Ranger
06-05-07, 08:30 PM
Ok, sounds like you had a relay stuck open so the fuel pump would not energize till you built enough oil pressure to take over and do what the relay was supposed to be doing. If it happens again, R & R the relay.

Not sure what to say about the "jolt'.

fpmesiIII
06-07-07, 07:46 PM
well I replaced the fuel pump relay with a known good one and I still get the hard hot starting. gah this is nuts. any other ideas?

Ranger
06-07-07, 08:05 PM
Hows the fuel pressure?

fpmesiIII
06-08-07, 07:27 AM
Hows the fuel pressure?

I dont have a specific tool to check the fuel pressure. but from the FPR, I did replace it with a new one thinking that would fix it. It currently holds a vacuum. but I have seen faulty FPRs hold a vacuum. maybe I just purchased a lemon. today I am going replace the FPR from my fathers 96 Deville and see if that solves the problem.

I do have a small gas leak somewhere near the gas tank. Would that have anything to do with these problems.

Ranger
06-08-07, 11:29 AM
Don't mess with your fathers FPR. If it holds a vacuum it is good. If you installed it wrong, it would be leaking. The leak should not have an effect. I'd get a fuel pressure gauge and check the duel pressure. Sounds like that is the only thing you have not checked yet.

fpmesiIII
06-08-07, 01:38 PM
well i just got the fuel pressure checked. he said it was good. it was at 45.

Ranger
06-08-07, 08:23 PM
I'm running out of ideas. Maybe it is not fuel related.

fpmesiIII
06-09-07, 11:34 AM
today I replaced the control module and all four modules. to see if that would be the problem. its wasnt setting off a code. so i dunno maybe it will help. just took it for a spin to see how it works. i still have a little jolt when coasting above 40mph doesnt seem as bad. ill go out in about an hour and see if it hard starts.

fpmesiIII
06-09-07, 02:44 PM
well with the new control module and ignition modules in it still hard starts. i give up, im going to resort the always valid. "it must be gods doing." thanks Ranger for your patience and knowledge. If it ever gets fixed ill let you know what fixed it.

Ranger
06-09-07, 04:59 PM
:banghead:

dkozloski
06-09-07, 10:19 PM
Crankshaft position sensors?

fpmesiIII
06-09-07, 10:21 PM
Crankshaft position sensors?

not sure never checked those. are they fairly easy to do. I have an FSM.

DevilleMN
06-10-07, 08:46 AM
Is the fuel supply line getting heat soaked, boiling the fuel, when shut off hot. Check if any sheilding or rerouting has occurred near the exhaust manifold or pipes.

What engine temps when this occurs?

Try opening the hood for a few minutes prior to trying to start hot, venting and cooling engine components. See if that helps.

What grade of gas? 87, 92?

fpmesiIII
06-10-07, 09:34 AM
Is the fuel supply line getting heat soaked, boiling the fuel, when shut off hot. Check if any sheilding or rerouting has occurred near the exhaust manifold or pipes.

What engine temps when this occurs?

Try opening the hood for a few minutes prior to trying to start hot, venting and cooling engine components. See if that helps.

What grade of gas? 87, 92?


the fuel line by the tank is wet when the car comes back from a trip and drips a few drops. i dont believe any shielding or re-routing has occurred near the exhaust manifold or pipes. i did install magnflow exhaust a couple years ago, but it hard started back then too.

it happens any where from 90-200

i use 87, i have tried 92 but it still does it.

weister42
06-12-07, 01:24 AM
I have the hot start problem forever and I've also replaced the FPR and checked the fuel pressure and everything checks out, the last mechanic told me all of my injectors are seeping gas - thus the hot start after it sits for an hour or so(engine is flooded with gasoline...I think), I just correct the problem by opening the throttle to clear out all excess gas.

Today however was different, I was on the highway doing close to 100mph then parked my car, about 5 minutes later my car started all unwillingly then dies, and I almost couldn't start it back up, just cranks and nothing. Eventually it started(I was pressing on the gas pedal all the way down) and it ran just fine all the way home. Yeah I'm going to install the set of known good injectors tomorrow and see if the hot start problem goes away or not.

btw my hard start problem started immediately after I installed my stereo, but I don't see how that would have anything to do with it.

dkozloski
06-12-07, 12:24 PM
Pull the stereo and see if it makes a difference. Anything affecting the communications bus can cause gremlins.

weister42
06-12-07, 01:00 PM
Pull the stereo and see if it makes a difference. Anything affecting the communications bus can cause gremlins.

I did and nothing changed. I left all the wires in but took out all the fuse so there aren't any power going through it. It's funny because when it first happened my check engine light came on, engine was running rough and got a misfire code, but after me driving it around for two mintues the rough idle and the engine light went away as if the car corrected itself. I really don't know what's going on but I'm going to put in the injectors today.

dkozloski
06-12-07, 03:49 PM
I did and nothing changed. I left all the wires in but took out all the fuse so there aren't any power going through it. It's funny because when it first happened my check engine light came on, engine was running rough and got a misfire code, but after me driving it around for two mintues the rough idle and the engine light went away as if the car corrected itself. I really don't know what's going on but I'm going to put in the injectors today.
If the stereo is loading the data bus, pulling the fuse won't help. You still haven't eliminated the stereo. Did you check out the Crankshaft position sensors? They are notorious for dying and hard start problems.