This is in regards to the '89 IROC in the sig...

Today, when I tried to start my car after having left it off for about 15 minutes, I found that it wouldn't start. I would turn the key, the engine had no problems turning over, and it actually sounded like it was going to run for about a second. Then, it bogged way down and died. I cranked it over again, and it sounded like it was going to run again, then bogged down for a second, then pulled back up again, then bogged back down, then pulled back up... and it did this in relatively even intervals, without me giving it any gas. I let it sit for a few seconds (to let the battery get its charge up), then tried starting it again, but this time I gave it some gas. All that did was to make the engine run up much higher when it sounded like it was going to start, but it still tried to bog down after a second (as if I didn't have my foot on the gas). I eventually got it started with my foot on the gas, and then when I took my foot off, it idled at a solid 1500 RPM for about 5 seconds, and then dropped down to a normal idle. After that, it got me home without any problems whatsoever.

I tried starting it again after I got home and waited about five full minutes, and it's doing the same thing.

I've never had this problem before, but I've also never really had to do much starting with the engine warm (usually I only have started it in the morning or after school or work, and in all cases it had time to cool down). Also, while it's never been consistiently "hard" to start even when cold, I do usually have to turn the key two times to start it (once for a few seconds--and nothing. Then again, and it starts right up).

Its not throwing any codes at me.

Any ideas what the problem is?

Thanks

 

i had a similar problem with mine, except it just wouldnt run. turned out to be the ignition module. as far as the having to turn the key twice, sounds like the starter solenoid to me.

 

Man, I didn't even think of that. But it makes sense, though--failing ignition modules tend to fail even more when they're hot. I also now remember having a similar problem on my '88 Camaro, and it was the ignition module. I'm taking it out to get tested when I get a chance...

RE: Needing to turn the key twice... This actually might be my doing. You know how you can always hear the fuel pump priming when you turn the key (assuming you have an electric fuel pump)? I have always waited until that sound stopped before I actually cranked the engine over--I always figured that I should "wait" for the fuel to get there before I start trying to use it. But, I've recently started to just turn the key all at once (like normal people do), and it seems to be more "willing" to start when I do that (i.e. it is more likely to start on the first try). I don't know if it makes any difference or not whether I wait...

Thanks for the reply!

 

Sancho,

'89 TPI? Does it start more easily if you apply a little throttle (about 20%) while cranking? If so, you may have an injector leakage problem.

 

Sounds like my problem... like Vader said, I diagnosed it to a leaking injector.

When the car's cold, it'll start right up- and stall. Does this for a while until I have a fit and put my foot in it to keep it from stalling. When it runs for a bit, the idle hunts like crazy (from high to near-stall) until it warms up even more; then it's fine. If it sits for 3-4 hours, it acts up again.

Used the GM service manual to diagnose it; fuel pressure dropped to zero instantly when the pump stopped priming. I thought the pump was bad- and I've replaced it twice already!! Went further into the chart... it had me check the fuel pressure regulator, which was okay, and it left me with "leaking injector".

I always wait for the pump to prime, too. If I don't, the car will crank forever... this usually happens when a hot chick walks by, and I jump the key from "off" to "on". But I haven't tried jumping the key when the car is cold. When I leave work today, I'll try it... BTW, I have a v6, 2.8, with multiport injection- MPFI is almost the exact same as your TPI (with MAF and cold start injector, too).

I actually yanked the plugs this weekend, priming the pump before pulling each one, and none came out "wet". I'm thinking it's the cold start injector; it's been in there for 249,000 miles.

 

Hmm...

Vader: I never start the car with any throttle at all--I've been taught that that's a "bad thing to do" with fuel injected cars. The only time I did it was just the other day when I was stranded in the parking lot. But, even when it starts "normally", I have always thought it was a little more difficult to start than it ought to be.

TomP: You've got the same engine that I was using--my '88 Camaro has the 2.8L engine. Interestingly enough, I can remember having starting problems with that car, and it turned out to be the ignition module. After I replaced it, the car started up perfectly every time--less than a second of cranking over and it was running. Never had any trouble starting since (although I haven't been driving it for the past month).

I also find it interesting that you thought it was the fuel pump with your car. I posted with the suspicion that it might be fuel related, and in fact I was getting ready to change it. But that's why I posted--didn't want to go mess with a fuel pump swap unless I had some second opinions on that!

So now I'm trying to weigh the likelihood that it's a leaking injector vs. a bad ignition module...

Just out of curiousity, how would I go about finding a leaking injector if, in fact, it turns out to be fuel related?

 

Well, I went ahead and just pulled the ignition module. I took it down to AutoZone to get it tested, and the guy at the counter told me that he couldn't test it. Of course, he could have been ing me--all he did was ask me for the year, make, model, and engine for my car, and then looked up the ignition modules in stock. When he pulled the screen up, he told me that he couldn't test it because the screen "didn't show a code" for the module. I know AutoZone has tested the ignition module off of my '88 Camaro (2.8L engine) before, so I don't know why they wouldn't be able to test this one.

Anyway, I didn't want to spend the money on an ignition module if I wasn't sure it was bad, so I went ahead and tried plan B, which was to find out if I had a leaking injector. So I picked up an Actron fuel pressure gague. I hooked it up, turned the key, and pulled 43 PSI of fuel pressure on the first try. I took the key out and watched the gague for several seconds, and the needle didn't look to be moving down at all.

So, I'm not too sure--I suppose the fuel pressure test rules out the leaking injector theory.

Does anybody know of another place that tests ignition modules?

 

Sancho,

You really need to monitor the fuel pressure for about 10-15 minutes. If the pressure has dropped significantly over 15 minutes, you may have a leaking injector.

 

Okay, I just went out to do a more long term fuel pressure test, and here are the results...

00 minutes: 41.0 PSI
05 minutes: 36.5 PSI
10 minutes: 34.0 PSI
15 minutes: 31.5 PSI

So there's definately some bleed off... but is it significant enough that it is really "leakage"?


BTW: Is it normal for the Schrader valve to leak when you take the cap off?

 

my valve did the same thing the first timei hooked the guage up to it. its not supposed to leak. all i had to do was get a valve stem tool and tighten up the actual stem inside the vlave.

 

Well, I just got home today and decided to check the transmission fluid level. I had to turn the car off to take my keys so that I could get into my house first. Came out with a rag to check the fluid level, tried to start the car, and it did the exact same thing that I originally posted about. Tried to run, bogged, tried to run, bogged, etc--for every other second, and then eventually just died.

Lucky enough to be home this time, I grabbed the fuel pressure gague and decided to test the pressure over time again.

The results...

00 minutes: 43.0 PSI
05 minutes: 26.0 PSI
10 minutes: 17.0 PSI
15 minutes: 11.0 PSI

I never got any replies as to whether or not my first results were "good" or not, but notice that my first test was taken at a time when the car would start; these were taken when the car wouldn't start. While I definatly believe these to be "bad" results, I'm curious: is it common for a leaking injector to only be problematic when warm?

For the record, I let the car cool off for an hour, and it started right up on the first try like nothing happened...

BTW -- Fixed the Schraeder valve; thanks 19WS6T/A91!

 

Sancho,

That is what you needed to see. You may have a leaking injector, or the pump check valves may be leaking back to the tank. It's also possible the regulator is leaking through a little. The good news is that you still have pressure at 15 minutes.

If you can charge the fuel rails, then carefully pinch the fuel supply and return lines, you'll be able to tell if you have an injector leaking or the pump/regulator is leaking back. You can use 'C' clamps or larger Vise-Grip pliers and a couple blocks of soft wood or short dowels (the key is to have NO sharp edges) to clamp the rubber lines shut on the left side of the engine, or use the special hose pinch Vise-Grip pliers. Once the lines are sealed, you should get no leakage back to the tank, and any pressure drop will definitely be through injectors or an external fuel leak.

Another thing you can do is to remove the vacuum line from the FPR while testing and watch for fuel leakage from the regulator diaphragm.

 

Vader,

Thanks for the response!

I get what you're saying about clamping the fuel lines, and I'm sure that could help narrow things down. But, I'm <b>really</b> reluctant to want to bend/clamp anything that's plastic or rubber under that hood--especially something that carries pressurized fuel alongside a hot engine. In my experience, if there's anything that's black and rubber/plastic under the hoods of these cars, it will break before it bends. If I get desperate, I might consider it, but I'd like to attempt to narrow it down a little further, if possible.

What I do know is that this loss of pressure only happens after the car has been running long enough to get up to/surpass operating temperature. What I also know is that there is a visible stain running down the side of my gas tank that appears to be originating from the top of the tank. Also, I have noticied that if I leave my car in the garage overnight, the whole garage smells of unburnt gas in the morning.

I don't know how much of that is relevent to the car not starting, but mabye that knowledge helps to narrow things down a bit. I'm just trying to figure out what my next plan of action should be...

--------------------------------------------------------------
On a side note...

I was actually getting ready to "simplify" things a little bit here and just get some new injectors off of Ebay but--surprise suprise--I got outbidded because another bidder clicked his button a few seconds before I did. This is the third time that I've tried to get some injectors off of Ebay in the past few months, and I have either been outclicked by a few seconds or outbidded by a couple of dollars each time. I'm getting very tired of the Ebay thing at this point, but I certainly cannot afford a completely new set of injectors.

Does anybody know of some other good places where I can go to get some LT1 or otherwise non-Multitec second-hand injectors?

 

A picture from beneath my car. Notice the black "stream" comming from the gas tank (at least I think it is). Might this be where the pressure bleed-off is going? (a long-shot, I know )

 

Sancho,

Your apparent leakage near the tank could be from several sources. In order to determine if the pressure drop is injector leakage, you can try applying about 1/3 throttle when cranking the engine when it is warm. This will admit extra air, and should not cause additional flooding. Some earler, less sophisticated EFI systems would apply fuel whenever the engine was turning and would base the fuel rate on the throttle position. You car won't do that while cranking, so there is no fear of causing problems by applying some throttle while starting to help clear a flooded condition. As a matter of fact, any throttle opening over 80% will completely cut off all fuel delivery while cranking, in a "Clear Flood" mode that was programmed specifically for that purpose.

 

i know this is an old post but i have the same prob kinda, 2.8l mpfi, when warm somtimes it doesnt start, bogs down like u guys cars, 1 thing i noticed is when it is having the problem my fuel pump doesnt even turn on!, so at first i thought it was the fuel pump, but its only when the car is warm so i narowed it to some sort of senser to do with the ignition, what controls the fuel pump??? i am thinking the problem is the ignition module i bought 1 yesterday and i will put it in soon, i will get back to u guys on the results, im going to check my fuelpresure too, i think my GF's dad has the equipment, ifnot how much to buy a presure tester?

 

aaroedg: You definately want to investigate why the fuel pump won't turn on--no engine will start regardless of what other problems may be present if it does not have fuel. My first guess would be the pump itself since a failing pump will often work intermittently (and I wouldn't be too surprised if that "intermittency" is affected by how long the pump has been running). Another possiblity might be an electrical gremlin interfering with the pump's power source, but I can't say that's a common problem.

To the best of my knowledge, there are no sensors which control the fuel pump, so you ought to be able to rule that out. When you first turn the key, the fuel pump primes for a set number of seconds--regardless of what any sensors are reading. You could pull the fuel lines from the fuel rail and the pump should still prime.

The ignition module is a good guess in the respect that, when they <i>are</i> bad, they often fail when they are hot. But, again, if the fuel pump is not acting as it should, the engine won't start regardless of what the ignition module is doing. If you really think the ignition module is bad, I'd suggest that you take it to AutoZone and have it checked.

I got my fuel pressure tester from AutoZone for $40.00 USD.

 

well i dunno if it is or not just last time it bogged down i turned th ignition on fer the 2nd attemp to start and no fuel pump?!?!?! does it only prime when the pressure is down? cause it might have turned on the first time i tried to start. i thought i could rule the fuel pump out beacause wouldnt it quit while driving not just while starting? thnx for the info

 

I'm not an expert on the subject but, as far as I know, the pump only primes based on a timed constant in the ECM; it's not dependant on how much pressure is in the lines, or if the fuel even gets anywhere. Like I mentioned, the pump will prime even if you disconnect the fuel lines. This is normal behavior before the engine starts.

It is also normal, however, for the pump to <b>not</b> prime if it has primed "recently" and the engine has not run. For example, if you turn the key to ignition and the pump primes, you turn the ignition off, and then turn the ignition back on within a short amount of time, the pump won't prime again. Again, I think this is based on a timed interval and nothing else (I think it's a 30 second interval).

Thus, it is possible that you thought your pump didn't turn on if it had already primed earlier.