racerseks

Okay, here's an update. I replaced my coolant temperature sensor...the one under the throttle body, next to the cold start switch...but the hard start condition persists. Then, I thought I might have found the problem. The harness going to one of the relays behind the battery was pretty chewed up, with some of the wires exposed and touching each other. I ordered both relays, and two new harnesses and replaced all of it...but to my surprise, no change. It's still hard to start. Here's what happens, before and after the new parts:

I turn the ignition on, and hear the fuel pump start. With my pressure gauge hooked up at the rail, the fuel pressure jumps up to about 43psi, but drops down to less than 20psi within a minute. When I crank it, it goes back up to 43psi and goes back down to 38psi and maintains that once it's running.

Is the cold start injector and/or cold start injector switch still suspect here? Any other troubleshooting suggestions?

Thanks!

aklim

Possible cold start injector but also FPR or somewhere in the tank. Need to clamp stuff off to see.

racerseks

Thanks...I replaced the FPR with the injectors. I guess that doesn't totally rule it out, but any way to test? No fuel coming out of it when I disconnect the vacuum line, and the pressure goes up a few psi when disconnected and running.

How about the clamping you mention? Is that outlined anywhere, and what will that tell me? Thank you.

aklim

If you fire up the pump and it drops, where is it leaking? Say you clamp off the return line and pressure holds, look at the regulator. If it still drops, maybe it is between the pump and regulator. If it drops after clamping the return line, I'd pressure the system and clamp off the feed line. If it holds pressure leak is between clamp and pump

racerseks

I don't see a leak anywhere.

Can you tell me where I clamp it off, and what I might use to clamp it?

Thank you.

bjankuski

The cold start injector or the cold start relay could be e problem. See if you have 12 volts to the cold start injector when you crank the car and make sure you have a ground. The cold start injector only operates when you crank the car so rule the power and ground either in or out.

Your fuel pressure is fine, rule this out as a problem. If you have 42 PSI at cranking, the fact that it drops slowly when it sits is a non issue related to the hard starting issue, when cold.

(I made an assumption that the hard starting is only when the car is cold, you should actually confirm when the hard starting occurs, cold or warm or both)

racerseks

Is the "cold start relay" the same as the "cold start injector switch" or is that something different?

Can you tell me how I check for 12v? I have a multimeter, just not sure how I use it to test this. Can you give me some "grounding instructions"?

It actually drops very fast before I even try to crank it...from 43psi to 20psi in less than a minute.

Thank you.

racerseks

I'll try it again tonight to confirm, but I'm pretty sure it's hard to start hot or cold...though it might be a little easier hot. Thanks!

bjankuski

Cold start switch and cold start relay are the same, I should have called it the cold start switch. Pull of the cold start injector connector and make sure one of the pins is grounded by using the ohm setting on the multi meter. Touch one of the connector pins and the intake manifold and see if it reads around 1 ohm, then touch the other pin and see what it reads, it should be open no reading. The pin that reads open should then read 10-12 V (switch the multi meter to read DC volts) when you crank the car. This will determine if you are getting power to the cold start injector when you crank the car.

The fuel pressure dropping to 20 PSI in one minute is not the issue unless you are getting a flooding condition when the car is warm. If you are getting 42 PSI at cranking you have fuel present and that is removed from the equation.

bjankuski

If the car starts easier hot I assume the reason for the hard starting is lack of fuel. To confirm this what happens if you put the peddle all the way to the floor and try to start the car (release as soon as the car starts)? This should turn off the injectors and if it was a lack of fuel the car should not start. If the car starts very quickly and clears out immediately it was too much fuel and that will cause us to go down a different path.

BlowerWorks

I have not re-read the entire thread so my bad if I mispeak here. Based upon a very quick analysis I'd say nothing to do with FPR etc. All to do with "chip" program and injectors.
What size injectors did you use ? Flow matched and confirmed ?
E-prom matches injectors ? greg

bjankuski

I agree, this is where I am heading but I need to rule out the cold start injector and then focus on the injectors/tune.

racerseks

Okay, I'll try that tonight and post my findings. Can you tell me what that will determine? Thank you.

racerseks

I have tried it with the pedal all the way down. Seems about the same. Will try again tonight though...

racerseks

I used 22lb Bosch III injectors from Fuel Injector Connection. I got a standard set, so not sure if they are flow-matched. How do I determine if the e-prom matches the injectors?

Thank you.

bjankuski

This test will tell us if we are getting power to the cold start injector. If we are getting power to the injector (When the car is cold) then we can rule out all of the wiring and associated trouble shooting of the cold start circuit. That would leave the cold start injector itself as the issue or the new injectors or the tune.

-If the cold start injector itself has failed you cannot get new ones so the fix for that is to add in the additional starting fuel with the main injectors, which requires a change to your tune.
-If the cold start injector is working but you still need additional starting fuel then you will still need that programmed into the tune to make it start faster.
-If the car is too rich then we need to go down a different path to solve the problem.

FYI adding in new injectors and then having this problem show up immediately makes me believe the tune/injectors needs to be adjusted to solve the problem. What most people fail to understand is the switching from factory injectors to aftermarket is not always a direct drop in and drive fix even if they are the same size injector. All injectors have a minimum pulse width and the tune needs to be adjusted to work with that minimum pulse width. If the factory minimum pulse width was shorter then your new injectors then the pre -programmed factory tune will be too lean at cranking and make the car harder to start. Once the tune is adjusted for the new injector pulse width this problem is eliminated.

racerseks

I need someone to watch the gauge for me, so it'll be a few hours before I can do the cold start injector test...but just to clarify, I am not getting 42 psi while cranking. It goes to 43 psi or so when I turn the ignition on, but drops to 20psi before I ever even crank the engine. Seems everyone mentions how it takes hours and hours to bleed down, and mine is so quick. Am I still barking up the wrong tree? Thanks!

aklim

I'd take off the fuel filler lid till I see pic below. Top line is feed, bottom right is return and the small one is the vent



Say you got someone to turn the key, pump runs for 2 seconds. Soon as he says he sees 40psi, clamp off the return line and see if the pressure holds.

slhawkins

Are you waiting long to crank the motor after building pressure? If you build pressure and then it drops to 20psi within ~5-10 seconds you're probably draining it to the tank. This usually happens when the FPR is bad or the pulsator at the pump. There's an FSM page or two for that problem, but it's essentially just clamping off the supply and return fuel lines just outside the fuel sending unit at the tank. If pressure holds when you clamp the return line, then it's the FPR. If it holds when you clamp the supply line, it's probably the pulsator. That's _likely_ an entirely separate issue and may not mean much.

I know it was probably a pain getting to that 4-way connector at the distributor - but would you mind trying the fuel pressure test with it unplugged and the car warmed up? At that point the cold start injector shouldn't be dumping fuel at all and the pressure shouldn't drop.

slhawkins

^That's what I was referring to, just a bit slow in typing it up. After that test, do the same to the supply line.