L98 Delphi injectors, long cold start?
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L98 Delphi injectors, long cold start?
I've read some accounts of long cold starts with the Bosch replacement injectors, anyone with the Delphi's from Southbend or whoever experience such?
Warm start is fine, no other issues, need to know if I should pursue it as a problem or not. 3-4 seconds cranking when cold and it sort of grudgingly
fires up but no weird idle or such. Fuel pump/pressure good, started directly after installing the Delphi's in my 86. Runs well otherwise.
Warm start is fine, no other issues, need to know if I should pursue it as a problem or not. 3-4 seconds cranking when cold and it sort of grudgingly
fires up but no weird idle or such. Fuel pump/pressure good, started directly after installing the Delphi's in my 86. Runs well otherwise.
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Being a 1986 then your issue is most likely your cold start injector switch is failing. It's responsible for activating the 9th injector for cold starts. Longer starts are the result of it failing.
Last edited by Red86Z51; Aug 24, 2025 at 01:29 PM.
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In my case, the coolant temp sesor didn't like the way I wired the pigtail into the new one. Guess it wasn't good enough.
That's on a '90, though. No cold start injector on a '90...
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Anything longer than about 1-1.5 seconds cranking time, I would consider to be a tuning problem. CSI or no CSI.
Here's an 89 Iroc starting up for reference: https://datazap.me/u/tequilaboy/feli...rk=13-24-23-14
This is a supercharged car with 42 lb/hr injectors running Shell V-power fuel in England. Not sure if there's enough spare ethanol in the UK to be wasted on automotive fuel, but that's another topic.
Note: it can be difficult to directly compare crank fueling between $32, $32B and $6E bins since you can't see the cranking fuel pw in $6E logs, and you can't see the csi injectors contribution in the earlier cars. You can compare the running fuel counters to get an idea of the actual cranking fuel delivered by the injectors, but the code and tables aren't exactly apples to apples between the earlier and later cars. They are closer than you think except for extreme cold temperatures (like -20, -40) but few C4s will ever be operated under such conditions..
You can blame it on the fuel or the tuning (or possibly the csi in conjunction), but I wouldn't blame it on the injectors.
Here's an 89 Iroc starting up for reference: https://datazap.me/u/tequilaboy/feli...rk=13-24-23-14
This is a supercharged car with 42 lb/hr injectors running Shell V-power fuel in England. Not sure if there's enough spare ethanol in the UK to be wasted on automotive fuel, but that's another topic.
Note: it can be difficult to directly compare crank fueling between $32, $32B and $6E bins since you can't see the cranking fuel pw in $6E logs, and you can't see the csi injectors contribution in the earlier cars. You can compare the running fuel counters to get an idea of the actual cranking fuel delivered by the injectors, but the code and tables aren't exactly apples to apples between the earlier and later cars. They are closer than you think except for extreme cold temperatures (like -20, -40) but few C4s will ever be operated under such conditions..
You can blame it on the fuel or the tuning (or possibly the csi in conjunction), but I wouldn't blame it on the injectors.
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Whelp, those are all solid suggestions and I appreciate it. It appears that some person that may have had a few more adult beverages than was prudent was present when I last assembled the TPI intake and such on this thing and did not quite fully seat the cold start injector plug
onto the injector.
After correcting that little faux pas it seems to start as normal when cold.
Now if this stupid vibration and slightly rough idle would go away it'd be great. I'm sure another four or five grand stuffed into it will straighten it out lol...
onto the injector.
After correcting that little faux pas it seems to start as normal when cold.
Now if this stupid vibration and slightly rough idle would go away it'd be great. I'm sure another four or five grand stuffed into it will straighten it out lol...
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In my defense it is annoying to fully seat down in there at that angle.
That thing dumps a lot of fuel when active, I had both injector fuses out and was checking for pressure drop from the CS injector
activating per the FSM and then stuck a noid light on it (which is when I noticed it wasn't plugged in fully) and after plugging it in
the motor started and ran briefly on just that injector. I wonder why they couldn't get enough pulse out of the other eight for
cold start till a few years later? Kinda odd to see non-mechanical EFI with a cold start injector.
That thing dumps a lot of fuel when active, I had both injector fuses out and was checking for pressure drop from the CS injector
activating per the FSM and then stuck a noid light on it (which is when I noticed it wasn't plugged in fully) and after plugging it in
the motor started and ran briefly on just that injector. I wonder why they couldn't get enough pulse out of the other eight for
cold start till a few years later? Kinda odd to see non-mechanical EFI with a cold start injector.
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Its very easy to get more cranking fuel pw out of the injectors by changing the crank fuel scalar and table values. I think somebody at Bosch was still collecting patent royalties on the CSI.
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