the bat wire measured 11.73 volts I'll have to find a ride to autozone and borrow a fuel presure gauge. Probably won't be until later tonight. If i pull #1 plug to check for spark what wire do i unplug so car doesn't start?

 

as far as listening for a vacuum leak i can't keep it idleing without feathering the gas

 

If someone else starts the car, you can use your hand to control the throttle linkage at the front of the TPI Plenum. You'll see two cables running on the drivers side.

If nobody can help you, then get a remote starter from Harbor Freight for $15. You'll want to put it on the solonoid cold, because it's a tight squeeze around the hot exhaust on the right or passenger side to get it on the terminal (the starter is below the exhaust manifold on the passenger side). That way, you can start the car from outside.

 

Pull the fuel pump fuse in your fuse panel.. Then your fuel pump will not run, so no fuel to the injectors. Crank the engine, check for spark. Reinstall the fuel pump fuse and then check for fuel pressure at the rail...

 

i pulled #1 plug and layed it on manifold cranked engine over and the spark was yellow. Then i checked the fuel presure at the rail with key on not runnig presure was 14 psi

 

Both verifications by yourself explain why your Corvette is running poorly.

No proper fuel pressure for required fuel delivery.

And no hot Bright Blue spark present.

Its a small wonder you even were able to start the engine in your '88 Vette.

Brian

 

so what is it i need to do next

 

When you were testing........

Was the battery up on charge?
At least 12.4 VDC?
12.6vdc ='s 100% charge.
A quick indication the battery was down on charge is if the starter motor was cranking or turning the engine over slower than normal, you can hear this of course.

Verify the battery charge is up to at 80-100 % percent.
Use your DVM multimeter with it set on DC volts.
Take a voltage measurement across the battery terminals.
Have a helper crank the engine over for you.
With the engine cranking over before it fires, you will see the battery voltage drop down to 10.5 - 9.6VDC.
That is OK...The starter motor places a heavy load across the battery when in operation.
Battery voltage should not drop below 9.6 vdc.
If it does, check the battery cable connections to make sure they are clean & tight.
If OK, Charge the battery for 30 minutes to hour with a 10-20 AMP per hour battery charger.
Make your cranking & static battery voltage check again.

Once you are sure the battery is fully charged and cables are clean & tight,
Remove a spark plug again and do a spark check again.
I like using a brand new spark plug gaped .035 - .060" inches for a quick check.
BRIGHT HOT BLUE SPARK MUST BE PRESENT.
If not, make sure the heavy Red or Pink power lead going to the HEI distributor is plugged in firmly.
I had the Power connector once come loose on my 87 Vert after I 1st purchased it in 2007.

Sometimes the Ignition coil will break down internally.
That will cause a weak yellow spark or no spark.
Other times the HEI module will start to fail.
Dwell time becomes erratic or there is no expanding ignition dwell from engine idle to 2,000RPM's.
If that happens the ignition coil will not be fully saturated or too saturated with primary current to fire correctly.
Poor ignition spark results and thus poor engine performance.

The fuel filter may be plugged causing low fuel pressure.
Replacing it is a good idea if never done before.
Not the easiest of tasks on a C4.
You may want help to do this.

The fuel pump is located right below the flip up fuel door.
Remove the door and you have access to the in tank electric fuel pump if the in tank fuel pump needs replacement.

Check the battery voltage 1st though.
If it low or near dead,
Testing for a hot ignition spark or fuel proper fuel pressure will not happen with accurate results.

Brian

 

The "yellow" spark could be the result of a low battery.. From all the "feathering" runs/starts that have been done, and that it is reported he had 11.7 volts when checking the BAT wire, I'll bet the battery is low.

Charge the battery and repeat the spark check. If it is still yellow, take your dist cap/coil to the Autozone where you got the fuel gauge and have them test the coil.

14 PSI on the rail is way too low... When you first turned on the key, did you see around 40 psi with the pump running for the 2 second prime cycle?

If not, like Brian said, the fuel filter could be clogged, the fuel pressure regulator diaphram could be blown, or the fuel pump could be weak or the pick up tube cracked.

Remove the vacuum line from the fuel pressure regulator and check for fuel or a very strong odor of fuel coming out of the vaccum port on the FPR. If it is present, it's a good bet the diaphram has failed..

I appreciate that you are making the efforts to solve this problem with limited funds, etc. Do you have any service manuals for your car? In your case, with limited funding, you might consider purchasing a Haynes manual at Autozone for about $20 bucks. It is nowhere near the level of the FSM, but it does give the basics, including most things we are suggesting... If nothing else, AZ will let you read through one at the store..

 

the battery is only 6 weeks old. i'm thinking maybe the bat volt may have been affected because i've had the hood and doors open off and on for a week now. I don't have a bat charger but i will check the bat anyway. will try and install a fuel filter tomorrow and again check the fuel presure afterwards. Is there a way to check the coil on the car?
Also would either of these cause it to backfire?

 

i will pull the vacuum line on the FPR as you suggest. Also will purchase haynes manual. Thanks guys for all your help

 

Yes.

I do not know the extensiveness of you auto & truck troubleshooting background.
I don't want to confuse the CHIT out of you.
Let me know if I am.

If I get too technical I may lose your understanding.

We live in a world of parts changers...........armatures and professionals alike.

To eliminate parts changing or swapping out parts I have to get technical and theory likewise.
That is when I lose or confuse many.

When working alone I can't confuse anyone.
Just myself

The old spark plug test with a fully charged battery is the easy test for you to do right now.

Changing out the fuel filter too.
Brian

 

Borrow the neighbors battery charger too.

He likely borrowed something from you recently.

 

Since becoming a certified wrench in the early 70's (yep, I'm that old), followed by over 25 years in aircraft maintenance/engineering, I just have to figure out what broke and why it broke before I change it...

 

my 35 years of background was in auto collision management. I'm not real technical in mechanical stuff and i'm afraid being 63 years old makes it even harder. I do have some tools but not everything thats needed. I also live in an apartment complex and that makes it somewhat challenging as the neighbors don't have tools to speak of either. I will do what i can and hope that i can get this monster running again.

 

LOL.

Managers past or present are very resourceful.

You have a very good inclination of what you are doing.

Just need a little guidance or help thats all.

There is nothing wrong with working on your Vette in the parking lot of an apartment complex.
I have done it in the past.
Most recently back in 2008.

I have even pulled engines and transmissions out of vehicles in the apartment complex parking lot(s).

At night when everyone was asleep.
Or the landloard was gone for a day or 2.

Just clean up your mess before he or she gets back.
Give the neighbors some beer to keep quite.

Brian

 

well it took 6 hrs to change fuel filter. i now only have about 10/11 pounds presure at the fuel rail with key on and not running. I took vacuum hose off at FPR and don't think i smelled any gas really hard to say since i smell like a fuel depot. I also charged bat and checked plug again still yellow spark. I do have 12.4 at the bat wire on distributer now. I actually thought i was hearing a ticking noise from the distributer? It is idleing now but still bogs down and backfires through the air filter

 

You are a brave person changing out the fuel filter on your 88 Vette without a Car lift or drive over pit to use.

Something does not add up to me yet.
You have a weak ignition spark and low fuel pressure at the same time.
I am wondering if you have a Power Feed problem to your Corvette's electrical system.
A massive voltage drop across the wiring to the Ignition circuit & electric in tank fuel pump circuit.
Perhaps a bad fusible link(s).

I want to you start your Vette and leave it running if possible in Park or neutral.
Take a voltage reading at the back of the alternator output terminal.
with the engine idling you should have around 12.6 vdc to 14.4vdc.
Then take a paperclip and backprobe the HEI distributor power feed connector(Heavy 10 gauge pink or red wire).
Connect your DC voltmeter Red wire to the paperclip.
The other end of the voltmeter connect to the negative terminal of the battery.
You should see near identical DC voltage reading at the HEI power feed connector as the Alternator read(within 1/2 dc volts).

If you do not see a near identical DC voltage reading then I am right there is a massive voltage drop due to a bad fusible link, decayed wiring & terminals, or a bad ground.

Let me know what you see.
The checks I want you to make now should take less than 1 hour by yourself or with a helper.

Brian

 

Make sure the paperclip is a Plain Silver metal style.
Not one of the colored plastic coated paperclips.

Unfold the paperclip to a straight wire with your fingers.
Paperclips make handy and easy to use electrical connector backprobing tools in a pinch.

Make sure to push the paperclip wire firmly up into the backside of the Main Power Lead Connector of your Vettes HEI distributor when taking a DC voltage reading.

I want the power connector plugged into the HEI for testing.
That way the ignition circuit is loaded with operating current in AMPS as normally operated.

Depending upon ignition coils used and engine operating peak RPM's,
GM HEI's will use between 4-7 amps current to a peak of almost 15 amps.

Brian

 

which one is the output on alt?