I'm pretty sure I made a seperate post on this issue but am having trouble locating it at the moment so I will start a new one.

When I first bought my 85 Z28 equipped with a 305 TPI, it did not exibit any problems with starting on It's own. I did notice that it seemed to struggle just a tad bit more from a warm start but everytime it would fire right up with the turn of a key. All that changed when I spun a main bearing in the original engine and installed a completely new longblock assembly. The car had been sitting in the summer heat for about 6 months with the dead engine, and when we installed the new engine attempts to fire it were foiled by a dead starter.

So we replaced the dead starter with a Duralast Gold from autozone (Yeah I know not the best of choice but I didn't have the money at the time for an Accel) and since the car was put back on the road it exibited bad starting issues. If you turn the key, mostly from a cold start, the engine will start to crank and you think It's gonna start but then it will just wind down and sit there and crank and crank and crank but not start. You usually have to do this 2 - 3 times before you will even hear a peep from any of the cylinders and it starts up. You can get it to struggle a bit and then fire up the first try IF you pump or hold down the gas pedal, which seems odd for a fuel injected car.

At first I thought either the cold start injector or the thermal time switch had gone south along with the starter, but I just read a post on here made by (I can't remember if it was krisb or kevin91z) that said the cold start injector only functions when it is below 45F. Even during the spring and summer heat the car still exibited this same problem. So If It's not the cold start injector, then what the heck is it?

The car does seem to start alot easier on It's own if you give it a few minutes to warm up, then shut it down and try to start it up again. But it doesn't always consistently do this and still sometimes needs a little pedal even from a warm start.

One other thing I noticed, is that after a failed attempt to get the engine to start on It's own, when you release the key you can hear fuel pump priming for what seems to be an abnormally long time (7+ seconds). Could this be in fact a bad cold start injector, perhaps stuck open and flooding the engine causing the difficulty in starting? I remember someone mentioning depressing the gas pedal acts as a "clear flood" to the ECM while cranking. Not sure about the truth to this however.

I tried grounding the thermal time switch, but this did not seem to change the pattern of abnormal starts any.

I am really confused at this point, and want to get to the bottom of this baffling problem. What could it be?

 

Once you build up some oil pressure, the fuel pump will run as long as the key is on. So it's not really priming, it's running. Priming only occurs for a couple of seconds when you first turn the key on. And that only happens when the key has been off for more than a few seconds. IOW, it won't necessarily prime every time you turn the key on, but it should prime every time you first get in and turn the key on.

You need to "scan" the ECM and see what the sensors are reporting. Your symptom is remarkably similar to a bad temp sensor that is indicating an abnormally low temp. This causes hard starting and flooding that gets harder the warmer it is.

 

Are you referring to the CTS? Come to think of it, my car has had a rich condition I have been trying to pinpoint since the day I got it...

When you say the fuel pump is always "running", this is obvious, or else the engine wouldn't be able to function. What I am referring to is the sound it makes while priming for about 2 seconds on initial key on. This is the prime. It makes this same sound again only much longer for 7 - 10 seconds after releasing the key from an unsuccessful start.

 

I told you why. The built up oil pressure from extended cranking is making the pump run. Do you have an oil filter with a check valve in it? There is no difference in "priming" and "running" other than the time at which they occur. On initial turn of the key, the ECM activates the relay making the pump run (prime) for two seconds. After that, the ECM deactivates it until the engine starts (or sees pulses from the ignition pickup IIRC). Aside from all that, there is a bypass route for electricity to get to the pump and this is thru the oil pressure switch. It completely bypasses the relay. I believe that is what is making your pump continue to run after your third attempt at starting it.

 

Yes you told me why but didn't tell me how.

Had you not mentioned anything just now about the bypass, I would still be scratching my head trying to figure out what the oil pressure has to do with the fuel pressure.

 

Have you figured this out yet? My 85 iroc has similar symptoms. It takes 5 seconds of cranking to start. Then runs perfect. I don't hear the pump running. Other strange clue is after 5 seconds of cranking it starts and the oil pressure guage stays pegged. It will drop after a couple minutes. If I turn it off and try again right away it will fire right up.
So to sum it up, why does it crank so long before firing. No codes are thrown.

 

Update. I do hear the pump run when the key is turned on. Cold start it fires right up.

 

I'm interested in this too. I've got '87 350 TPI which does almost the same thing. Takes a solid 5 seconds before it will consider starting, but after its been up and going, it starts instantly, no problem. Also, the same as Nick's problem, my oil pressure gauge is pegged until a couple minutes later.

 

Fuel Pressure regulator.

 

I've read these engines have to turn over 8 to 10 revs before the ECM turns on the injectors. On my 88 I've found I can turn the key on, wait a couple seconds, hit the starter for a couple revs, let off the starter and then hit it again and the engine will start right up. For the original posted problem I'd suggest a fuel pressure check to see if any injectors are stuck and bleeding off, flooding the engine. But even so the first cold start of the day might not be affected. A bad coolant sensor might well be the culprit. Look for a sensor with black and white wires to it.

 

Fuel pressure at the schrader valve is 38 psi after the pump primes, and 32 psi at idle. No fuel in the vacuum line to the regulator

Nick

 

I did a little more checking. With the fpr vacuum line unplugged the pressure at idle is 42. Plugged in it is 34. Looks like the pressure is ok. Next i am going to ohm check the injectors.

Nick

 

I just did some follow up on mine, fuel pressure is 42psi after pump primes and holds steady, at idle the pressure drops to 38psi. The injector resistance measured 16.4-16.5 ohms for the 8 primary and 4.2 ohms for the cold start, should be good. I tried checking for 12V at the connectors with the key on, but didn't register anything. I must not have done it correctly? Is there a way to check the cold start switch? I can't remember.

 

After some running errands today I checked the injectors. All 8 tested at 17 ohms exactly. Maybe I am going in the wrong direction with mine and the hard starting isn't fuel related.

Nick

 

I don't think its the cold start injector or regulater at all. I have an 89 tpi that has the exact same problem and these didnt come with the cold start inj. When cold it takes 5-10 seconds to start, after warmed up it starts just fine. Good pressure, brand new regulater, bosch 3 injectors, basicly everything fuel related is new except for the pump. Havnt replaced the pump because pressure is good! Everything electricle is new as well....

Been trying to figure this out for ever with no resolve. Fixing to break down and buy a new pump for the hell of it. This is absolutly rediculus that we are having these problems. I know for a fact it doesnt take this long for a tpi to start as I have been around them forever and never seen them take so long to start up when cold (or when sitting over night)

However I did read some articles about a rubber cross-over tube on the pump inside the tank that falls apart over time causing other problems and symptoms. I dont see how that could cause our problems but......its worth a look, a very long, uncomfortable, tank yanking look!

keep the ideas comming, seen this exact same problems in another thread and nobody figured it out and the thread fell off the earth. I think we all want this fixed once and for all...

 

When cold mine fires right up. When warmed up if it sets for more than a couple minutes it takes a solid 5 seconds of cranking to start. Rpms jump to 1800 then begin to drop to idle. At no time does it ever run rough.

Nick

 

Did you try putting a bit of starter fluid in it? Check ecm if its firing the injectors. Get some noid lights to test your ecm...mayb the ecm injector drives puked

 

Don't know about these other guys but my car has a fairly new ecm. I doubt that thats the problem, however, it's definetly worth a try because you can rent noid lights from almost anywhere and get money back when returned. Thanks for the idea......keep em coming.

 

Try the lights, ya i would only change fuel pump as a last resort...but sounds like your pump is ok

You had the same problem as i had, but mine started right up with a bit of fluid...

 

Guys, can a bad ESC module be causing this?

I read that while cranking, the ESC controls the timing until 400RPM and the ECM takes over.

The reason I think it may be something with the ignition circuit, is because I pulled codes last night and got 42 which I have never seen before. Last week something else strange also happened. I went out on lunch break to start car. As usual it didn't wanna start. But this time was different. Even with the foot on the gas, it just sat there and spun with not a single cylinder firing, and the whole time the car had a steady bounce to it like a misfire. After 3 times of this, I was about ready to give up and call a towtruck when it was time to go home. The 4th try, it decided to start up. Hasn't done this since.

Before we dropped the new engine in this cold start problem was exactly the opposite. On a scale of one - ten 10 being the worst and 1 being functioning normally, cold start was a 1, warm start was a three. Now cold start is about a 9 and warm start I'd give a 4 and sometimes 5.

 

did you try the ICM mounted in the dizzy? also how is your oil pressure? there is a switch mounted above your oilfilter and if your pressure isnt making it up or the switch is bad it will also kill the fuel pump, i doubt it's the ESC module, but ANYTHING is a possibility, also how do your injectors test with an ohm meter?

 

I doubt oil pressure is an issue. It seems fine when running and It's never been an issue. Tomorrow I will keep an eye it while cranking. The entire longblock assembly is new so the pump and switch should be good.

As for the ICM, this is located inside the distributor cap right? I have two spares and suspect this might have been a previous problem since I got them from the PO when he sold me the car.

Earlier I managed to test all but the 5 and 7 injectors and they all checked in at 17.5 +/- 0.3

 

chiming in on this one since my car just recently started having this problem. Would the MAF sensor have any bearing at all on ignition?
Who can outline what sensors matter when ignition happens so that we can follow that guidline to find the problem?

 

Still fighing this on mine also. Figured the car is 20 years old so I went ahead and replaced the whole ignition system, pulled dizzy, new pickup coil and ign. module, new cap and rotor, new coil, new plugs. Still has the extended start when cold. Pump, regulator, and pressure are fine. Now I'm wondering if the summer blend oxygenated gas might be the problem? Sure is something going on.

 

I doubt its the oil pressure as well, as stated before mine is doing the exact same thing as the original poster stated..........ALL my sensors are new as well as the ignition control module in the dizzy and various other components including an oil pressure sender because I thought the same thing as you.........Its got me stumped and I am a certified technition with many years of service including diagnostics, very weird indeed. I have a friend at the local oreillys here that will let me plug a new ecm in and see if that works, he will take it back if it doesnt......most auto parts stores will not take it back...........Im gona try that and let yall know what happens.

I am interested in what the person above me states about the esc controling timing, going to look further into that as well.

 

How many years/miles on the injectors? Might be time to either replace them or have them cleaned and flow tested.

 

Brand new bosch 3's in mine.....even rebuilt and cleaned the fuel rail when I bought them and installed a new adjustable fuel pressure reg. Played with fuel pressure all over the place and still nothing.

Im tellin ya'll, basicly everything has been replaced on my car minus the fuel pump (witch has good prime, running, and WOT pressure) and the ecm. I'm saying this because I want to save some people some money and figure this crap out without people spending thousands and just throwing parts at them.

Now, with the fuel pressure on my car statement. Heres something to think about, when you put a big intake and big carb and high flowing heads on a run of the mill 350 without upgrading from the original stock mechanicle fuel pump........you will have good "PSI" going to the carb on the gauge.........but the fuel "volumn" will be too low to support the new mods, (motor will fall off at high rpms). If you dont get a high performance high volumn mechanicle fuel pump such as holly makes........your killing your performance.

I dont know maybe Im just rambleing BUT, possibly the old pump is a little weak and the volumn is too low but the psi shows correct.......IDK!

 

I haven't checked in on this thread in awhile, but here's my update in case it helps someone. I have an '87 IrocZ, L98, I was having a COLD START problem, in that it would crank for 6-8 seconds and not start. I'd wait a few seconds and try again and then it would generally start up on the second try. After warming up it would start immediately. My injectors ohm'd out just fine, fuel pressure good, new plugs/wires. This weekend I replaced my cold start switch while doing some other work and it started after several cranks on the first attempt after the replacement. Can always check to see if it fires up when you squirt some fluid in the throttle body, this helped to convince me it was a fuel related problem.

 

just got a walbro 255 in the mail today, will be installing it soon, will let yall know if it helps the cold start issue....

 

good news fella's, fixed the problem, and i would suggest yall do this too.

Put a new walbro 255 in, replaced all the rubber fuel hoses for the tank, and removed the pulsater on the fuel send line on the pump assembly, the pulsater is not needed at all. One of the three fixed the problem, more than likely it was either the fuel pump or the pulsater causing the problems as my fuel hoses where not that bad at all.

I said it before, and i will say it again, my old fuel pump was just fine.....well, at liest it tested just fine, it had 38-40 psi priming pressure, 43 psi idle pressure, and 49-50 psi wide open throttle pressure......this is perfect for the tpi, somebody had replaced my pump before and it tested just fine on all levels, there was absolutly nothing wrong with it yet, replacing it with the walbro 255 and removing the pulsater fixed the problem.

And before you ask, I have a bbk adjustable fuel pressure regulater, and I had bumped it up a bit for some higher pressure.......even with the old pump, on the new pump it likes it about 50 psi WOT, and about 43 idle pressure, this is not any different than I had it on the other pump, and like i said, before I put the new pump in I tryed the fuel pressure at many many different psi's and nothing helped the problem.

So, I strongly recomend removing the pulsater and installing a walbro 255 pump, it is a high volumn high psi pump but that is what the regulater is for, so for those of you who have bone stock tpi's, you can still put this pump in with no problems at all, and the best thing is it will support up to 600 horse power levels, so it gives you room to do lots of mods.

I hope I can save some of yall lots of money and lots of trouble throwing parts at your cars, while this may not fix everybodys starting issue, I am fairly certain that it is most of everyones problem, good luck, and let me know if you have any questions.

Im so glad this problem is fixed, because mine was so bad I was wearing out the teath on starters and flywheels tryin to start the damn thing in the morning.