hi guysthis is for the z28 in my sig, which doesnt belong to me anymore, but im posting for the new owner. before having sold the car to the guy, the car was experiencing a 5k rpm miss. in other words, itd fall on its face above 5k rpm. which was not normal. before the miss, itd pull hard till 6800rpm. (the buyer knew about this when we made the transaction).

so the guy called me today telling me hes trying to start the car and it wont start. i heard it over the phone, its cranking but not firing. what should i check first? im supposing its either ignition or fuel related (duh). another thing that happened to him though, he was out driving it and the car just stalled on the highway. then wouldnt restart. then a day later it fired up (although now it doesant at all).

my one friend said it sounds like a fried opti, i myself was thinking fuel pump.

#1- how to check for spark? (i suppose if theres spark that the optis alright then??) do you check for spark by pulling a plug (still plugged into the wire), and cranking the motor? if theres spark its fine??

#2- if #1's not it, then i guess ill go buy a fuel pressure tester to see if the motor's getting the right psi. question again, how do you do this? what is the proper psi? what is the right and wrong way about doing this?

im gonna go through some searches on here myslef as well and see what i come up with. id really appreciate the help thanks

 

any thoughts?

 

Hi,
Your idea about pulling a plug and watching for spark sounds good to me, just make sure it's not touching anything that it will potentially arc to.

I don't have any suggestions about the fuel pressure.

Good luck.

 

Guess what i had this exact thing on my dad's Chevy Express Van the other day....(does it sit outside?). But anyway she would roll over and could hear the pump pressurize the system.

first thought was ignition, cause she wasn't firing at all.

Next i think to myself hmmmmm this is weird it was just drove the other day--ignition stuff doesn't just usually go out totally and won't fire at all.

So i am like man i don't want to work on that thing.........so i take a break for two days.

After the couple days i'm like hmmm you need air to fire right? So i pull the intake off and MAF and TEMP sensor and she fires up first try

Take the filter out clean it plug the sensors in and then the "check engine" light comes on. So i decide just to drive it a bit.......and check engine light goes off..........Runs perfect now!!!

 

If it sat outside try it^

 

Whoops sorry didn't see that it was missing........forget what i said......lol

 

IMO ... it's the opti... so check your spark ... i would almost be positive its your opti

what mileage?

 

coil wire

 

thanks for the help so far we did change the coil wire before hoping that was the culprit, but it wasnt.

im thinking fuel pump
my buds thinking opti
did a quick search on here the other day, someone having had a similar problem, and replacing the icm fixed it.

i didnt get to go see the car today, going tommorrow morning.

person who asked about the mileage:, should be about 80k or so now. yes, original opti and fuel pump.

i do have a spare opti i bought off someone on here last year, but im not even sure if it works or not, so i wouldnt be too crazy about going through the work to put it in (although, i just might).

the main reason im leaning towards the fuel pump beeing bad is cause of the 5k rpm miss it had. from various other searches i did on here (6 months ago), the 5k rpm miss was mainly traced to a dying fuel pump or a bad coil wire. replaced the coil wire to no avail.

and , to further my case on the fuel pump, on 2 occasions before the car was sold, my gas tank was nearing empty (not quite there, but lets say it still had 40 miles in it), the car wasnt starting. put some more gas in it, and it fired up.

my "magic touch" may get it to start tommorrow (and god only knows how bad i need to hear that rumble again), but we will need to pinpoint the problem and remedy it.

ill check the ign. fuses, fuel pump fuse, test for spark, check fuel pressure.

i dont suppose just pressing on the schrader valve would be a good indication as to wether the fuel pressures right , would it?? if gas comes out, its fine? if not, no? i dont think so but just checking.

anyone know the proper psi, and the proper procedure for testing it (with a fuel pressure gauge?).

thanks as always

 

Fuel pressure should be 41-47 psi at idle with the vacuum hose to the regulator removed or the same pressure when the system is pressurized and the engine is not running. At idle with the vacuum hose on, pressure may be in the 35 psi range.

 

thanks captain

i just dug up my haynes manual as well. it says the same thing

so:
1-check related fuses (ign+fuel)
2-"listen" if fuel pump is operating
3-check pressure
4-check fuel pump relay in kick panel


now this part im not too sure how to go about:

5-check for spark (pull a plug, hold it with pliers i suppose, and crank the motor??, or ground it to something?)

if all that checks out, it would seem that the opti would be the one to blame, correct?

anyone know how to use a digital multimeter as well?? bought one a few weeks ago, and might be put to use nowwhat setting do you put it to for what? seems complicated, but im betting its pretty simple lets say to check the fuel pump relay: do you use the black wire? the red one? both? what setting? etc. any ideas?

EDIT: forgot to say thanks

 

To check for spark pull off a plug wire and put an insulated screw driver down by the end of the wire. You should see the spark arch across the gap between the screw driver and wire. You can also go buy a spark checker at an auto parts store. I got a cheap one at Checker, you just ground one side, then put the other to the wire. It lights up everytime spark goes by it. Check all the ignition fuses. For the fuel pump attach a guage at the schrader valve on the back of the fuel rail under the cowl. Pressures should be what Shoebox mentioned above. If it still doesn't start it could be VATS related, but you should not be getting any crank at all for a VATS problem. If you have a scanner the opti will throw high and low res codes, you could check for those.

 

a spark checker is a good idea i really dont think its a VATS problem. so the opti will throw codes without illuminating the check engine light? hmm, didnt know that dont have a scanner though thank you everyone for the help. we'll check it out tommorrow and see what comes of it. have a good one

 

If you hear the fuel pump coming on when you turn the key and your pressure tests are good, you don't need to check the f/p relay.

When you check for spark with a plug, you have to ground the metal body of the plug.