davidj3594

I'm having a no start issue.I've checked the ECM fuse and it's good.I also checked the fuel pump relay and it's good since I can hear it turn on.yet I can't hear the fuel pump prime.the ECM is working since I get a code 12.before starting the big task of dropping the rear end to replace the pump I wanted to try this but I'm not sure witch one it is or what exactly it does.is it behind the distributor or on top of the oil filter?my oil pressure used to bounce around so I'm preety sure it's bad.i was feeling around behind the distributor and I touched a cable and now it says no oil pressure on the gauges so that mght be it.any help?
Cars is an 87 350 tpi iroc

hockinjm

Does your car crank over or do you get nothing at all?
If you can get underneath your car you can locate the oil sending unit fairly simply. Look by your oil filter area.
My Oil sending unit is almost bad, but should not cause a no start.
Can you check fuel pressure?

DENN_SHAH

iTrader: (1)

the oil pressure switch is only a backup in case the fuel pump relay fails and it isn't designed to supply power to the pump long term.
just because the relay clicks doesn't mean its good.
the contacts may be bad and not allowing voltage to flow across them.
i recommend checking for power going into and coming out of the relay with a test light.
if you have power from the relay, next i would check for power as close to the fuel pump as possible. if its ok, check for a good ground from the sending unit.
you may have a fuel pump prime wire, its a single wire with a female connector and normally it breaks out of the harness near the fuel pimp relay or near the battery.
you can put power to this wire and if the wiring to the pump, pump ground, and the pump are good, the pump should run.
also, in the ALDL connector, with a test light terminal G can server the same purpose to check for power to the pump or to supply power to the pump with a jumper.

davidj3594

ok the car does crank over.just no fuel since it will run a short while with starting fluid.I can barely get underneath the car since the previous owner thought dropping a car to a rediculous level is cool(parked during two fast two furious ***** era)it involves using two jacks first one of those really small ones then once it's lifted I can get my bigger Jack in so I'm kind of fearful of getting underneath it.I know it probably isn't the relay since i switched it with the maf burn off and still no pump.I even tried the fan relay and that one is less then a week old.Where would I find the ground for the sending unit and what color wire is the fuel pump prime wire? Can anyboy post a pic?

davidj3594

A little more info....
Car was parked for two years due to a failed theft attempt.steering column was wrecked.dude got sick of it sitting In The parking lot(ruining paint and developing a little 1/4 rust due to snow melting in the trunk).he put it on craigslist and I got it cheap enough to where it didn't matter that it needed work since it was exactly what i wanted(red,l98,iroc,and t tops,with g92 factory).any way I bought it replaced antifrezze and oil along with stearing column and it ran like a top.nice smooth idle and tranny shifted great.I used it for three months as a daily driver to and from school I put a little over 1500 miles In these three months never leaving me stranded or showing any singhs of trouble.now the 3 month permit ended and I decided to park it to redo the interior . So it sat for four weeks I would started every week up until the last two weeks.so I go to start it the fourth week and it struggles to start missing a couple of times but it finally did start and idled correctly.as it was idling I decided to Install the lower plastic panel and I heard a spark about 2 minutes later the car died and. it wouldn't start(turned out the spark was the ground for the courtesy light that was loose).And that is where I'm at now

sofakingdom

iTrader: (1)

Shoot some starting fluid into it.

Does it start?

Go from there.

Don't outsmart yourself. Keep it simple. See my signature for an example of mental simplicity.

davidj3594

Have and it will start with starting fluid. Do you mean to keep It runnig with staring fluid for a while in case the pump decides to start running?
Forgot to mention the day it stopped working the tempeture dropped well below zero.

sofakingdom

iTrader: (1)

No; if it starts with starting fluid, then you know you have a fuel problem. Pretty simple.

Doesn't matter that it was cold one day. Lots of cars work fine on lots of days when the temp is FAR below zero. Your grandma's old carbed car even managed, way back in the CIvil War days. Not an issue.

The fuel pump relay supplies power to the pump. Particualrly during priming. If it doesn't work, the pump won't work. Therefore I'd suggest starting there. A good place to divide the system in half, and chase from there toward the problem, instead of running around in "maybe it's this, maybe it's that" hell.

A relay is nothing more, or less, than an electrically operated switch. It has a coil which is an electromagnet, which makes a piece of iron move when it gets magnetized by having power applied; attached to the moving piece is a contact; when it touches the stationary contact, it's just like turning on a switch. It's a mechanism for allowing a very small amount of power to control a much larger amount. That's it. Simple.

You should have 2 small wires going to the coil, which if you put your multimeter across them, should have 12V across them when the pump is supposed to be running. 12V across the coil? Yes/no? Yes: ECM and all wiring looking back toward it is all good. No: problem is in that direction.

You should have 2 large wires going to its contacts, one of which brings battery to the relay, and the other takes it to the pump when the relay gets turned on. If you have power to the coil, and power coming in, then you should have power going out. Yes/no? Yes: wiring to the pump, or pump. No: relay.

It's just a car. Doesn't get much simpler. It's just electricity. About the easiest part of a car to understand because they're built so simple in that area. Don't outsmart yourself, don't let it outsmart you, you can DO THIS. Be LOGICAL, and RATIONAL, and THINK. You can do it.

ZZ3 Z28

Let me try to add a couple things to the mix since I had a similar problem recently. I am at a disadvantage since I have a carb car so my experiences may not exactly fit with a tpi car. Noentheless, all cars are pretty much work the same way.

I took two pictures to help with the oil pressure switch idea. The first pic shows I have two oil pressure switches. The one on the left is original to the ex-LG4 motor and the one on the right is a new one for the ZZ3 motor. Both work in the same way, if you have oil pressure, the contact is closed and a signal is sent to allow the electric in-tank fuel pump to run. May I assume you have some sort of circuit on your tpi?



The second picture is the new switch with the cap off showing the two conenctors that can be jumpered with a paper clip that tricks the system into thinking oil pressure is satisfied allowing the fuel pump to run. The ignition key has to be in the run position--not start- for the circuit to be completed.



On my car, I can hear the fuel pump run when this switch is jumpered. I get my 6 psi of fuel to the carb--I have an in line fuel pressure gauge right before the carb--and I get fuel to the bowls. Like I said, I am not too familiar with tpi cars so I don't know if this excatly pertains to you but I think in the end, it all works the same.

In your first post, I think you said you didn't hear the fuel pump running. I think if you jumper the oil pressure switch out completing the circuit, the fuel pump should run, or at least you should hear it. If you don't hear it, then I would vote for a bad pump.

If you think your fuel pump is operating but don't hear it, then try disconnecting...well this may be tricky since tpi cars have a higher fuel pressure, right...to see if you have pressure out of the fuel line. If I disconnect my fuel line at the carb, and jumper the oil pressure switch, I get a nice flow of fuel, not a dribble. Remember to get a canister or someting to catch the fuel. Don't disconnect the line and just shoot fuel all over.

You also said something about a spark. Sparks, flashes, the smell of burning wires are always bad. Can I ask, the car was an aborted theft, did the previous owner jumper something out to get it to start since the ignition column was tampered with? You said the spark was when you were replacing a under dash panel? Look around down there, do you see anything strange? Can you smell anything? Was there a flash and was it from under the dash?

I think what sofakingdom said upwards there is a good description of how to go at this. Don't over think it it. And most importantly don't introduce a new problem that wasn't there in the first place.

davidj3594

Bought the sensor from autozone that in your pic but mine only has two contacts.I'll try jumpng them tomorrow to see if the pump will start when jumped.if Itdoesnt I'll get back to you.the whole column was replaced from gearbox to stearing wheel and that worked good for 3 months as a dd.Thanks for all the info guys.I'll keep trying and get back to you tomorrow

DENN_SHAH

iTrader: (1)

thirdgens sit low even when they were new. add 20 plus years of wear, tear and carrying the weight of the car around and the springs will collapse causing it to sit even lower.

sorry, my book doesn't give the color or exact location of the fuel pump prime wire.
usually its red, but it can be gray. but it may be missing which is why i mentioned terminal G in the ALDL.
no need to jumper the plug at the oil pressure switch, you can use terminal G in the ALDL to supply power to the pump.

projected life for a fuel pump is ~8 years. some don't last that long, others last longer.
i didn't say it before, but odds are the fuel pump is dead.
but a problem with the wiring is possible which is why i said to check for power and ground. at the sending unit, the ground wire is black, the fuel level sender wire shows to be pink, the power wire shows to be gray, but could be orange.
there could be a problem with the sending unit it self, the pins in the connector can become loose over time and burn up. its something to check if it comes down to pulling the tank.

also, if you do indeed have a bad fuel pump, there may be a part called a pulsator on the sending unit that connects the fuel pump to the sending unit. if your car has it, throw it away.
use the fuel hose that comes with the new pump.

also make certain they give you a pump for Tuned Port Injection because it is a high pressure pump. Throttle Body Injection uses a low pressure pump that will not put out enough pressure to even start a TPI motor. just by looking at the 2 pumps, you can not tell one from the other.

sofakingdom

iTrader: (1)

The oil pressure switch isn't required to start the car... THINK ABOUT IT... there's no oil pressure then anyway.

Use logic, and avoid this left turn into the weeds.

Focus on the relay circuit instead. THAT'S the one that starts the car, not the OPSU one.

ZZ3 Z28

Tan is the wire color off the single-wire pressure switch, and the two-wire switch has a tan wire and red wire.

I don't wish to get sidetracked with lengthy descriptions here since we're still trying to troubleshoot a friend's car, but on my ZZ3 there is a fuel pump relay that cuts off power to the electric fuel pump if the oil pressure is lost. I would assume that any car that has an electric fuel pump has such a circuit to prevent motor damage in case of oil pressure loss. My Z28 has been modified from a mechanical pump to an electric pump so not everyone will have the same application. I understand that some vehicles only had an idiot light on the gauge cluster which did not shut the car off if pressure was lost.

To break it down to the most basic level then, in my car, if that connector comes loose from the two-wire oil pressure switch, my fuel pump does not run. In most cases this would make me believe that the fuel pump is dead requiring a fuel tank removal. But in reality, it is not a dead fuel pump, it is a disconnected wire.

This is why sofakingdom's post #8 is important. Is power being satisfied to the fuel pump?

And here is what also can happen even if you hear the pump running. In my case I could hear the pump whining but was getting no pressure at the carb. The reason why was a disintegrated hose connection at the pump that connects the pump to the metal fuel line. The red circle shows the bad hose line next to the connection.

DENN_SHAH

iTrader: (1)

maybe this wiring diagram will help clear up how the system works from the factory

davidj3594

Okay I've come to the unfortunate conclusion That it is more then likely the fuel pump.the last time it started it strugled quite abut to hold idle and it just wanted to die unless I kept pumping gas then it held idle for a short while and then died(which should have been my first clue but with how gm desgned these cars you have to be absolutly sure so that you don't end up dropping the rear end for nothing lol) jumped terminal g on the adl and no pump.relay is working.and just to compleatly remove the doubt,so there is no way a bad oil sender can cause the car to not start?by the way I have the one that is shown to be original to the lg4 engine in zz3 z28's pic.after messing with it my car no longer wants to show any oil pressure when I try to crank it,it's just all the way down.I'm probably gonna be replacing it but not till I switch the fuel pump,which is why I asked if it could cause the car to not start,I don't want to end up replacing the pump and not be able to start the car.

davidj3594

So just to clarify a bad oil sending switch won't cause a no start issue?right?

sofakingdom

iTrader: (1)

No.

Cannot possibly.

Does your car have any oil pressure before you turn the key?

Then how could the OPSU possibly prevent it from starting?

One way or another, it HAS TO BE possible for the car to run, BEFORE it has oil pressure; eh?

It's just LOGIC.

How did your voltage tests at the various points in the system turn out? Was the relay being told to operate by the ECM at all times that it's supposed to be? (wire 490 orange in the schematic, terminal D of the relay) Is there a supply of hard battery to the relay? (another orange wire, probably larger, terminal E of the relay, wire 340) Was 12V being supplied by the relay at the terminal going toward the pump? (terminal A, tan/white wire # 120) Did you then find the 12V at the Fisher Body connector?

antoine

Just put a fuel pump in it.

davidj3594

12 volts all around thanks for the help.your quote makes a lot of sense but after all it is a thirdgen fuel pump and everybody tries everything before getting into the pain in the as it is to change it lol.


It never hurts To try the the simpler things before getting into replacng a third gen pump,especially in below freezing weather with no garage,and a refusal to cut a whole In the floor like a r3dneck.but yeah I'm putting in a new fuel pump.btw does anybody know why the fuel sender is so expensive?I got quoted 188 dollars from advance and it seemed high to me.there's a 305 tpi in the scrapyard,can't I use a brand new fuel with the sender from this car?

Firebrat

I'm having this identical problem, already replaced relay. Where exactly is the terminal 'G' you are referring to?

Firebrat

Where is 'G', can you please post a picture on this?

OrangeBird

iTrader: (1)

It is on the "ALDL" (Assembly Line Data Link) , commonly called the "OBD1 port" , located under the dash about 4 inches to the right of the steering column . If you search "ALDL pinout" or some such , it will reveal threads where you can find the letter designations for all the terminals on the ALDL .