85 C4 fuel presure problem

[lovehatec4]

last week I upgraded my 85 C4 with the bosch 3 type injectors. I also installed a new presure regulator at the same time. My fuel presure is about 42 psi at Idle and the car runs and drives fantastic in every way.
Here's the Issue...the car takes longer to start and when cold much,much longer. Yesterday I put the fuel presure gauge on my C4 again and started then shutdown the engine. I watched the presure drop from 42 psi to 5 psi instantly and then it slowly went to zero in about 30 minutes. I then started looking for fuel leaks and found no problems. Can anyone help me with this?

[ChuckG]

Have you put a voltmeter to your fuel pump?

Did you replace the regulator diaphragm? They can get weak.

[lovehatec4]

Thanks for responding. Fuel pump is new and yes the regulator diafrahm was replaced with a new one when I replaced the injectors..I reused the original regulator cover (non-adjustabe) type. I'm wondering if there is a one way check valve in the fuel pressure regulator or somewhere else in the fuel system that could be causing the problem. I'm also thinking maybe the regulator could not seating correctly. I just hate the thought of tearing this thing down again.

[c4c5specialist]

HI there,

I would definately be looking at your cold start injector and switch to make sure its not shorted ON or not at all.

Drivers side, in the center of the lower intake is the injector.

Allthebest, c4c5;

[lovehatec4]

Thank you for your response. I'll look at that today and get back to you.I guess I discounted the CSI because It runs so well. BTW, is the fitting/coupler that is just under the fuel filter a check valve?

[lovehatec4]

Thank you c4c5specialist. You were exacly right... It is the cold start Injector. After checking for voltage problems and finding none, I then pulled the feed line from the back of the left side fuel rail and vacume tested it. Definately the problem.

[lovehatec4]

I cant find a new cold start injector.Does anybody know where I can get a new one? (85 C4)

[ChuckG]

My idle is sketchy. I should check my CSI too. My money is on vacuum lines, but better to check everything. It does gasp for either air or fuel on WOT.

If you find the part, please post the source. Always good to know where to look for odd parts GM no longer has in inventory.

Just checked: Zip has the switch for $74, but no listing for the injector

[lovehatec4]

Thanks for responding. If I don't fint the CSI,I'll just cap-off the fitting on the fuel rail and put a vacume plug on the the feed line to prevent a vacume leak or debris from getting in the line. I'm in SE Texas so cold starting isn't so much an issue for me.
About your sketchy idle,, remove and clean the IAC then readjust per factory insrtructions.(I Have the instructions if you need) When you finish that,check your TPS voltage at warm and correct idle for .54 volts. Also since you said you have a wot issue,while you have the voltmeter hooked up to the TPS and correcly set to .54 ,turn engine off,,then turn the key back to the on position...Slowly move the throttle to wide open and back to idle while watching the volts. The volts should climb incrementaly to just over 4.0 volts then back down to .54 (shouldn't have any dead spots).I just did this to mine when I fineshed the injector project and WOW what a difference.
Anyway, thanks again and I hope all is well.

[ChuckG]

I'm with you on the cold starts. My car is in storage Oct through May. Still, it has been getting chilly in TX. My old man lives in McAllen. Must be the Global Warming.

I do periodically check the TPS. It should be okay, but one never knows. Our roads are like a pioneer trail anymore. Maybe something got jarred.

I'm thinking vacuum problem or maybe my cam is too much for the throttlebody. It's a mild grind, but it's only a 48mm TB too.

Still, I have spanked an '09 Bullit Mustang with "secret parts" (I asked if one was a boat anchor??) and told him my car was dead stock. That was fun!