Hi Guys,
Finally got around to installing my fuel rail pressure guage yesterday.
I have been having a hard start condition for the last year or so when the car is warm. If I alow it to sit for more than say 6 hours or so, it will start right up. If not, when warm, it will start after 5 to 8 cranks and then puffs some smoke...

Last night, I took the car home after 30 minutes of driving and noted the fuel pressure when I reached home. With the engine off, it read 45psi and appeared to be holding (or so I thought).
10 mintues later, it had dropped to 27 psi. 15 mintues after that, it had dropped to 15 or so.

So in total, 25 mintues and the pressure was at a little less than 15 and still dropping. I think I'm leaking fuel into the chambers when warm causing a rich condition upon startup-only a guess though.

Otherwise, the cars runs very well, perfect idle and power is good.

Can anyone offer any insight?

Could it possibly be my regulator or is this an injector.

The car has approx 110,000 miles

 

ttt

 

ttt - again

 

What is the pressure on your gage when you turn the key on but don't start it?? Should be 36/40 PSI. The fuel pressuire bleeds down after you shut the engine off, it will not hold pressure forever.

 

40PSI +/- 2psi. There is definitely fuel there. My concern was that it may be flooding itself.
The problem only occurs when it sits for a few minutes while warm engine off. On restart, it'll crank for a while and finally start (and puff smoke). When cold, the car starts right up. Could this be oil contamination?

 

Most likely it's leaky fuel injector(s).
The only way to know for sure is to pull the rail with injectors out of the intake manifold with the feed and return lines still connected. Then prime the system and see what's leaking.

It's unlikely your regulator unless you find fuel in the vacuum hose for it.

Your smoke may be you burning off the excess fuel that's sitting in the cylinder.

 

I would suspect leaky injectors. I had a similar hot start problem all last summer. i just replaced the stock Rochester injectors on my 88GTA (55000mi on them) with Accel injectors. Hot start problem is gone and I gained alot of low end back.

 

Sweet. Thanks...

 

When are you suppose to pull the vacuum hose? After it was running?

 

Yep. Or during.

 

Injectors are a good chunck of change aren't they?

 

$230 for new Accel's.
Stock injectors seem to be a fairly common problem on our cars.

 

Hmm, thats not all that bad. $230 and an evening of tearing the TPI off, not a bad deal for no smoke and better perf.

 

I think you can find them cheaper at Hanlon Motorsports.

 

heck, as many miles that are on it and the time frame I plan on owning it, some basic stock ones will do me for a another few years.

 

Same thing happened on a friend of mine's car. VERY likely injector leaking.
Send 'em off to TPIS in Chanhassen, MN and get 'em cleaned and flowed instead of buying new ones. If one or two don't flow close to the same as the rest, they'll substitute injectors that DO match. It's worth it.

 

Where exactly is this vacum line?

 

here's a test to determine where the bleeding off is coming from. this is pretty much a 2 person deal. get a pair of vise grips or some way to pinch off the rubber lines. while running have someone shut the car off. as soon as they do that pinch off the supply line. it will be the one with the larger metal line attached to it. if the pressure bleeds off then it's either regulator or injector. if oyu pull the vacuum line off the regulator and smell or see fuel in it, then that's the culprit.

now if the pressure didn't bleed off start the car again. now have the person shut the car off. as soon as they do this, pinch off the return line. the one attached to the smaller metal line. if the pressure bleeds off, then it's the check valve in the pump.

 

a very common problem on these cars when there is a hot hard start problem is the fuel pump check valve not holding pressure.When the pressure is lost the fuel starts to boil in the fuel rail <thats the thing that holds the injectors ib place> sitting ontop of that hot engine.Cranking the engine over enables the fuel pump and when the pressure gets high enough it clears the boiling fuel in the rail and it starts.An easy test is too attach a fuel pres gauge and watch the pres as you pinch off the RETURN line to the tank.If the pressure stays steady with the return hose pinched the trouble is the fuel pump check valve. 350 tpi using the high output factory pump seems to be prone to this problem.

 

I really hope it isn't the pump. It's only 2 years old (less than 6,000km's)!!

Thanks for the info! I'll do those tests tonight and see what happens.

 

sorry i forgot to add that 1st see if the pressure is dropping off...then build pressure up again and start pinching hoses.....be careful not to cut the hoses or damage then by pinching too hard or with sharp tools.

 

My readings were as follows. At shutoff, fuel pressure was 43-44 psi. After 25 mintues, pressure had fallen to 14psi. Is this the cause of my problem?

I'm going to try and pinch the return line tonight and see if it start normally. If so, I'm gonna be pissed.

WAIT
Can you guys clear that up. One of you says if it bleeds, it's the check pump with the return line pinched.

The other guys says it's the check pump if it doesn't bleed off when the return line is pinched (which makes more sense to me).

Please clarify!!!

P>S> I'm showing 45 or so PSI with the vac line connected and the engine off just after shutdown.

 

do this........turn engine off and pinch the return fuel line....watch the pressue gauge.....does it drop off?..........if it does NOT drop off release the pinch on the return line and see if it drops off.There are 3 ways the system can loose pressure ! leaking injectors...2 leaking fuel pressure regulator 3 fuel pump check valve leaking back.Its easy to check each one with a pressure gauge...........i'm gonna give you a good way to test if its a fuel pressure problem causing the hard start trouble.Get the engine hot......let it sit turned off for 15 mins<is that when it gets hard to start? and is it cranking over ok just not starting>then without starting the car turn the key to the ON position until you hear the fuel pump stop running.Then turn key off wait 20 seconds and do it again..........do it 6 times.....this should clear any fuel boiling in the rail..............now try starting it.....does it start right up? if it does then you have a fuel pressure leak down problem causing the hard start.

 

I'm still betting on a bad injector or two being the source of the problem!

 

Tired , I hope you're right!! My fuel pump was only installed about 2 years ago (less than 10,000km's ago)!

I'd hate to change the injectors cause I plan on going with a 350 HO or scoggin dickey motor in the future.

 

Ok, I primed the system and then crimped the smaller fuel line which I hope is the return to the tank.

Fuel pressure dropped off just as before. In 5 mintues, it had dropped approx 10 PSI.

I guess this eliminated my fuel pump check valve and leave the regulartor and injectors (I hope)

 

i have to apoligize for my STUPID BRAIN cells dying early!!!!let me give you the proper info.........to test the fuel pump check valve prime system and pinch off the LARGER hose......if pressure stays up its the check valve in pump leaking.You tested the regulator by priming and pinching the smaller hose.So you only need to do a few more tests.......remember its possible for multiple devices to leak....so check everything.

 

Thanks for the info:

Just to be clear.
I'm testing the two fuel hoses that come off the front of the TPI and come around on the drivers side.
When I crimped the smaller one, there was still quite a bit of drop in psi. Does this mean my regulator or injectors are toast?

If I crimp the larger line, I'm pretty sure it will raise the psi on my guage though. Not sure...

 

the small line is the return to the tank from the regulator.......the large line is the feed line from the pump.

 

let me try to explain all this.......if you pinch the large line and pressure stays up....the fuel pump check valve is bad,If you pinch the small line and pressure stays up ....the regulator is leaking back.If you pinch both lines and the pressure drops.....the injectors are leaking.I hope this info helps.

 

Thanks for the clarification. I'll try this again tonight.