warm start - have to hit the gas

98inSFl wrote:

Codith, I am with Albert, you have a loss of prime or leaking down fuel pump or something, you need to put a fuel pressure gauge on it and watch whats going on while cranking, a slow rise in fuel pressure rather then almost instantaneous pressure will do this., What happens if you cycle the key a couple times waiting 2 seconds in between?

I already checked fuel pressure. [There's another thread about this somewhere I think but initially I would have bet it was a fuel problem because this started happening about the same time I put the walbro fuel pump in, which bleeds off pressure as soon as the pump cuts off. However I've already replaced it with a new and properly set up racetronix pump and I confirmed it with a fuel pressure gauge.] It operates exactly like stock - primes up quick and holds pressure.

What are the chances of an injector or 2 leaking fuel into the cylinders when it sits, and how would I find out which injectors?

The car would kick out a black cloud every time it was difficult to start if injectors were leaking.

I was finally able to get a fuel pressure gauge and a scanner on the car. Key on, engine off, I have 50 lbs. running is 44 lbs. It holds pressure after the car is shut off for at least 5 minutes, and dropped to about 30 in a half hour. I don't know the recommended specification for that. I had no trouble codes, but I did get a slight voltage reading (about .2) from the O2 sensosr with the car shut off. I still suspect a leaking injector or 2. The car runs fine, it just seems like I have to step on the gas to get more air so it will clear out. It starts right up if I shut it off and start it again, the problem is when it's sat for about 15-20 minutes.

Your fuel pressures look good and the fact that your still holding 30 psig after shutting the car off for a half an hour confirms you do not have a leaking fuel injector.
At least not something bad enough to cause your problem.
My fuel pressure bleeds off faster than that and I don't have a starting problem.

SupersportSteve wrote:

I was finally able to get a fuel pressure gauge and a scanner on the car. Key on, engine off, I have 50 lbs. running is 44 lbs. It holds pressure after the car is shut off for at least 5 minutes, and dropped to about 30 in a half hour. I don't know the recommended specification for that. I had no trouble codes, but I did get a slight voltage reading (about .2) from the O2 sensosr with the car shut off. I still suspect a leaking injector or 2. The car runs fine, it just seems like I have to step on the gas to get more air so it will clear out. It starts right up if I shut it off and start it again, the problem is when it's sat for about 15-20 minutes.

I admit I'm pretty much stumped by this one. I'd consider taking the car somewhere for diagnostics. Then again... you may want to remove the MAF and throttle body and clean them again. You may opt to have a dealer or mechanic do it for you; for instance the GM dealer near me has a solvent tank just for dip-cleaning throttle bodies. Don't know if it is ultrasonic, and doubt it needs to be. Also, consider getting new gaskets to replace the old ones. Little air leaks will be small enough not to keep you from running but will cause all sorts of silly problems. Finally, remember that the TB is a precision device and has to be handled carefully. Don't force the parts. And as usual this advice is at your own risk and worth what you paid for it...

Here is a quick refresher: there are in general 2 ways to clean that throttle body. One-if you don't pull it-is to clean the throttle plate (butterfly valve) and it's surrounding bore of accumulated soot and varnish. Do this by first lightly spraying cleaner on the butterfly valve and surrounding bore. This will loosen the crud. Then scrub the crud off with a toothbrush moistened in the cleaner. Next wrap a thin lint-free (try microfiber) towel around the head of the toothbrush and use it to wipe up the mess, leaving the throttle plate and surrounding bore clean. The engine should start right up because only minimal amount of cleaner were used. Do not spray the throttle plate and intake area behind the throttle plate heavily with cleaner, because this causes hard starting and may damage nearby parts like the throttle position sensor.

The other way -if you decide to pull the throttle body, then remove it as instructed in the factory service manual. You should wear chemcial gloves (nitrile) for this, and work in a well ventialted area. Once off, using a shop rag (that microfiber rag) soaked with throttle body or carburetor cleaner, remove any carbon build up from the entire throttle body bore, butterfly plate and idle air control shaft. Use that old tootbrush to clean the corners around the plate. If using a spray cleaner, spray just into the tight spots around the plate. Be sure to also clean the entire top and bottom surfaces. For stubborn deposits, the cleaner can be left to soak for awhile; as a "cleaning tank" you can use a small disposable aluminum roasting pan or some such. If you use the tank approach, get a bottle of the TB cleaner from your GM dealer. Once clean, use compressed air to blow-dry the TB. Reinstall (duh!).

Albertj

I removed the throttle body and cleaned it and cleaned the MAF sensor, So far, the problem hasn't been back, but it's only been 1 day.......my fingers are crossed.

How dirty was the TB?

Also--did it look like it'd been already pulled? Maybe it was sucking wind... ?!?

Albertj

The throttle body was very dirty, I totally disassembled it and made it look like new. I doubt it was ever cleaned. I did find a split vacuum tee. I put some gasket sealer on it until I can find a replacement. I didn't clean anything in the intake, although it looked like it could use it.

For myself, if I am sitting and the idle "hunts" in park, it's probably time to clean the throttle body. However, with a botttle of straight Techron in the tank every other oil change (winds up being once a year) I am not sure how long to go between pull-and-clean cycles - I've been doing that (the techron thing) since pulling and cleaning my TB over 50,000 miles ago and the idle's not hunting yet. I bet it's kind of dirty by now though - but if it's not symptomatic I'm not likely going to pull or poke it unless I am deep under there for some other good reason.

Let's see how you're running in, say, a week or so.

By the way if you can tell me where that tee is, I might be able to find a PN and post it. Sometimes the numbers are molded on and sometimes not. Some tees are unobtainium and have to be 'faked' from common parts and adapters (with a little black silicone sealer to make sure the contraption does not leak). HELP section in Advance Auto usually has a good selection *and* the older stores often have even more in the stacks--if you get a good counterperson he or she can usually find one that can be made to work.

Vacuum problems really suck (ha ha).

Albertj

I connected another known good battery and a charger on top of that to give it a boost in voltage for cranking. I saw about 12.5v while cranking (more than ideal on a healthy battery alone) and I started crankin it. It's a no-go. With it cranking faster, it did a little tiny bit more but wouldn't fire up beyond a couple really desperate putts after I stopped cranking. So it's not a system voltage problem. I guess I'll try the fuel pump jump idea tomorrow (today technically) but I really don't think that's going to do anything. The pump was pumping stronger than ever with the extra boost in power and it turns right back on after the prime cycle as soon as you start cranking it over anyway so I don't think preventing the prime end from happening is going to do anything. I'm to the point where I'm thinking about putting the stock injectors back in and putting IFR's back to stock to see what that does. I wouldn't mind so much even doing the work but I'd have to make my old injectors usable again which I don't know if I can even do since most of those bottom plastic oring retainer pieces are all cracked or broken off. Anyone want to lend a brother a set of good injectors?

I have had the hot start problem for a while also, decided today to test the FPR, with the vacuum hose off the regulator I tried to start car and saw gas spurt out. Replaced the FPR with a used one from Morad that I got the last time the hot start problem appeared. Problem seems to be fixed now. Now I am wondering what took me so long to change it out. Must have been the 100 degree days.

I have been having the same warm start problem for about 6 months and it's been getting worse. The car starts fine cold, but is a pain to start when warm. It's best if I let it cool to below 180 degrees before I try to start it again. Also, the car runs fine going down the road - seems to have plenty of power. We have replaced Cam and Crank Sensors, Ignition Control Module, Evap Purge Solenoid, Cleaned the MAF and TB, checked for vacuum leaks, checked the FPR and it's good. The fuel pressure at the GM dealer read 18 - 30 lbs, and we got 30 - 40 lbs of pressure when we checked it so I guess the next step is to replace the fuel pump which I've been dreading due to the expense. I just wanted to say how much I appreciate your posts, this thread and this forum in general. You guys are my best resource!
Katrina

Did you check fuel pressure with the engine off? The fuel rail will sustain pressure for some time, for the next start. If you have a leaky injector, it could be losing pressure, maybe causing a hard start. Just an idea.

AA wrote:

Did you check fuel pressure with the engine off? The fuel rail will sustain pressure for some time, for the next start. If you have a leaky injector, it could be losing pressure, maybe causing a hard start. Just an idea.

I asked and was told that yes we did check the fuel pressure with the engine off. He also checked the injectors for leaks.
Thank you for your ideas. We are fresh out of new ideas. I will be happy to have this on-going problem solved.

Suggestions:

Check the wiring to the fuel pump at the tank and see if the connection is dirty/intermittent.

In a pitch dark area (must be about too dark to see) start engine and look under hood with light off. YOu may see coronas around the plug sires. If you see any replace the wires. Don't get crap wires - get OE Delco wires, Magnecors, Taylors or some such -- Riv ignition is high energy and will electrically bust ordinary wires. Matter of fact the symptoms you talk about sometimes (often) pop up after someone replaces plug wires for "maintenance" with an inexpensive set.

Again, check the motor mounts.

If you need instructions on any of this please search the site or ask.