88 L98 manual. I’ve been chasing this hard start issue for months, and I’m running out of ideas. It cranks for about 8 seconds without touching the throttle until it slowly catches, fuel pressure is good soon as key is on it jumps to 42psi and will drop to 38 or so when it finally starts. I replaced Cold Start Switch, 10.6 volts at distributor when cranking, also rebuilt distributor, replaced both MAF relays and new MAF for good measure. Cleaned up as many grounds as I could find. When it finally starts it runs fine, and will fire right up when warm if it doesn’t sit for more than 15 minutes, after 15 minutes it still struggles to start but not as bad when stone cold. I have tried the clear food mode, but it makes no difference. the way it fires it seems like the ignition isn’t firing right away. Wondering if the oil pressure switch is the issue, because I’m running out of options at this point. Thanks for any suggestions

I have a video of it starting and it’s to big to post here.

 

Does the hard start correspond with fuel pressure bleeding down, 15 minutes?
Oil pressure switch is just fuel pump backup power, if you hear your 2 second pump @ KO primary power is OK.
Plugs old ??
Can you do an injector balance test ?? (cheap injector tester).
Timing OK ??
Fuel 93-94 octane ?
Air filter clean ??
.
.
.

 

The fuel pressure is fine, as soon as the key is on, it jumps to 42psi.

Not sure what you mean about hearing my 2 second pump at KO ?

New injectors, new plugs, cap, rotor, distributor rebuilt (new pic up, module, coil). Timing set at 6 degrees.

Good fuel and air filter. It runs fine, and will start right up when hot and it will start somewhat easy after sitting 15 minutes or so. Its just an issue when stone cold.

 

The way it starts, after 8 seconds of cranking, it slowly catches, chugs a little bit, then slowly comes to life. No smoke or smell of fuel, and once it’s running, it is fine.

The reason why I was thinking maybe the oil pressure switch, is if it’s defective it might not read 4psi right away, and the more it cranks it finally reads 4psi and the engine fires ?

 

When you first turn the key to (KO) the on position you should get 2 seconds of fuel pump, that is the (ECM) primary power for the fuel pump. The oil pressure switch is just a back up. My question about fuel pressure was is it bleeding all the way down to zero in 15 minutes, how long does it hold fuel pressure ?
Which fuel injectors were installed ?? The cold start injector gets it's voltage directly from the starter circuit, is the CSI getting voltage? Make sure the connector is pushed well up onto the injector.

Pull the PCV hose off the intake manifold, squirt 2 seconds worth of starter / brake fluid into the intake and then PUT the hose back on and start it up, this will check if it is a fueling issue.
You could also try several 2 second short cranks and see if that makes difference.

It idles perfect when running correct ??

 

Thanks for the help !

Pressure holds in the rails for hours, the injectors I installed are the “stock” Bosch 22lb injectors

I have not checked the CSI, I will do that when I get home today.

I will also try shooting some starter fluid into it.

Yes it idles perfectly around 750-800 rpm once it starts, and runs fine.

I will post back later this afternoon and see what happens. Thanks again.

 

That idle may need a TPS adjustment if the voltage it too high. My 87's TPS voltage should be 0.54 vdc ±.08
If not, I would look for a vacuum leak. Make sure the bellows between the MAF and TB are air tight.
Maybe venture into an IAC adjustment.

Above 95° the cold start valve is not used.
.
.

 

Just to mention, above 95° f the cold start valve is not used. I see your are in St Pete.

 

TPS is at .56v, no vacuum leaks, bellows are tight, it has a new IAC (though the way they’re making parts, it could be faulty). Yeah it’s pretty warm here, but I’m near the coast so it doesn’t get above 93 most days and the car is under a carport.

Car hasn’t run for 2 days so it’s stone cold, I squirted some carb cleaner into the PCV inlet on the TB, didn’t seem to make a difference, it maybe fired up a second earlier than a normal cold start. It did the same chugging to life for a couple seconds then it was running and idling fine. I let it run for a few minutes then shut it off, let it sit for a minute and it fired right back up. I checked the connection to the CSI and it seems tight, I guess my next thing it to check voltage at the CSI when cranking it cold ?

 

Do you have the ability to see data ?? Also , the water temp of the cooling system (CSI switch) would be when 95° ends the CSI, maybe get the water up to temp and see when the hard start occurs. These engines stay warm for a long time.

 

I don’t have the ability to see the data. The car fires up easily most of the time when the engine is warm. Well, I know that when I get the car up to 230 degrees and let it sit for 6 hours, the hard start is back, it will crank for 8 seconds then slowly chug to life. I have a video of it during the hard start with a fuel pressure gauge hooked up, it’s too big to post here, but maybe I could PM it to you ?

 

What do I need to pull the live data ? I have been getting the codes with a jumper wire, once and a while I get the annoying 36 code, but right now the codes have been cleared

 

A free PC based program like WinALDL or Tunerpro and about $70 in worth of parts (an OBD1 ALDL connector with 10K resistor) https://obd2allinone.com/products/aldlobd1u.asp . There is a lot of fake junk on the market and only a couple real ones, most are just fancy paperclips. Data is limited on OBD1 cars. Your car sounds like it is having a basic problem of fuel, air or timing, something data on OBD1 is very limited on. If it is a basic problem and seeing data may be of limited help so I am hesistant to cause you to spend $70.

It would however be nice to see what your coolant temp sensor (intake manifold near cold start switch) is reading.

You might try disconnecting the timing wire and see how it runs.

It was timed with the EST wire disconnected right ?? Sorry you probably already know that.

What started all of this ? You can PM me but the file may to big. Can you post video on Youtube ??

If you put your foot to the floor and crank it over is it a smooth ryhthm / sound, like all the cylinders are the same ???

Your 100% positive there are no vacuum leaks . EGR diaphram OK, no code 32 ?

Throttle body clean ??

What was your plug gap ??

.
.

 

JM2cW..my money would be on the CSI. I have an 87, had the same issue it turned out to be high resistance at the connector caused by a "little bit" of corrosion. Because it it restarts fine after initial start up i would really look at the CSI.

 

I was wondering how much data could be obtained from a OBD1 system. I guess I will hold off on that for now, but thanks for the info.

Yes, EST was disconnected when timing was set, and cleared the codes afterwards. It runs like crap with the EST disconnected

This has been a on going issue since I bought it a year ago, it pretty much sat for 12 years. Though the previous owner did start it once in and a while and he said it would have an issue starting once and a while. I drained the tank, and installed a new fuel pump, strainer, fuel filter, and injectors, and it still ran and started the same as when I bought it.

Tried sending you the video but it’s to big, will try and see if I can compress it.

Are you saying pedal to floor while I’m cranking it ? I’ve never done that, but I have tried the “clear flood mode” and it doesn’t help. I don’t smell gas, and the engine runs fine once started. Though it does ping under load when above 220 degrees using 93 octane, so not sure if the advance is too much, but that’s another issue.

EGR is a new OEM GM part, but it has thrown a code 32 after a few hundred mile highway road trip, figured it was the solenoid, so just cleared the code, and it never throws the code 32 when driving around town.

TB is pretty clean as far as I know, I took it apart months back and cleaned it out and replaced the IAC while I was in there, and afterwards it ran fine but still had the same hard start issue.

Plug gap is .035 and I’m using Iridium plugs.

Thanks for the help so far, I’m not giving up on this car.

I think I’m going to look into the CSI tomorrow and see if it’s working, might as well try and eliminate another possibility.

 

Thanks, I think I’m going to look into the CSI a little more, I never thought it really came into play living in a very warm area.

 

""Are you saying pedal to floor while I’m cranking it ? I’ve never done that, but I have tried the “clear flood mode” and it doesn’t help. I don’t smell gas, and the engine runs fine once started. Though it does ping under load when above 220 degrees using 93 octane, so not sure if the advance is too much, but that’s another issue.""

The pedal to the floor "clear flood" is sometimes used to keep the engine from firing so each cylinders compression can be heard. If they all have nearly the same compression it is a smooth ryhtm. I think pinging is concerning. The advance system is made to keep that from happening.
.
I am putting together a simple WAV file of my 87 L98 cold starting with the CSI disconnected. You can hear how long it takes to start as well as the smooth rythm each cylinder has.

I think it to be a timing problem, admittedly, I am running out of ideas to help you. You are positive your timing is good?? Who / what was rebuilt on the distributor ?? Have you double checked that all the connectors on the ditributor are plugged in well??

Please listen to the below WAV file and excuse long blank spot as audacity and windows 10 was a pain to edit on so skip to 1.0 minutes. One CF member who has installed iridiums as a professional remarked to me that iridiums are fine for a perfect running car but does not work well with an ill car.

1. It was started with me standing outside of the car.
2. The throttle was never touched
3. Has not been cranked in at least 24 hours.
4. Radiator was at 79° and car is inside my 79° garage.
5 CSI was unplugged at the injector.
6. This car has a slight rough idle, so it is not perfect.

 

OBD1 / ALDL scanning would tell you everything you need to see for diagnosis. Id be interested in what the coolant temp sensor under the throttle body is sending to your ecu.

 

I scrolled this whole thread looking for a mention of coolant temp sensor. This is where my bet is.

 

I did in appx my 5th post and @VikingTrad3r did also.
""It would however be nice to see what your coolant temp sensor (intake manifold near cold start switch) is reading.""