My stock 87 350 is having a very hard time starting. Here is where I'm at:

When I bought the car, it came with this problem. He said replaced MAF but did not help. When I turn the key, the pump does not spin all the time, only very seldom. I have replaced the relay and did not help much. I do not get the 2 second prime. Only when oil pressure rises do I get it to start. I don't think that it is the pump because it does work but something isn't tell it to start. I got two codes prior: 34 and 54. The MAF relay was not plugged in all the way so that cured 34 and a new relay cured 54 but the car does not perform and the SES light is still on.

My question is this: how do I jump the relay? Tan-Red?

Any other help would greatly be appreciated.

 

im having the same trouble. i always thought that when u start a tpi it should start at the first turn of the key but i have to hold mine for like 3 to 4 sec??? i have two codes and they are the vss and the egr? any help??

 

the fuel pump relay is ng// the oil pressure switch on the engine also runs the fuel pump. if the oil pressure drops it shuts the pump down. buy building pressure it turns the pump on over riding the fuel pump relay. IMO

 

but if the car is not running how would it have oil pressure? to me it sounds like ur saying that if my oil pressure is low then my fuel pump wont work on startup??? im confused

 

So the switch could be the culprit in my case. Also, the oil pressure sending unit is brand new but i'll look into the switch, But i thought the swtich only works when the car is on, not start up...

 

Also check the wiring connection to the fuel sending unit by the read end. My 89 IROC would all of a sudden just sputter and cut out. It left me on the side if the road a few times. I put a new relay and new pump in and then found out it was a simple bad connection.

 

I agree with this. Bad fuel pump relay is most likely. Spinning the engine builds enough pressure after a while to close the switch and power the fuel pump.

 

when you crank the engine the oil pump is building pressure.. if you had a manual guage on the engine you will see about 20psi.. change the FP relay,,

 

To update and clarify this post, DJ and I have been working on this problem but have yet to resolve it. The issue is that there is no "2 second" prime upon starting the engine cold, the car cranks for about 10 seconds or until oil pressure biulds..then fires. Also on a cold start, with the fuel pump "primed" the engine will crank but not fire and acts as described above. Once started the car runs like a bandit with no issues at all, car restarts on the first turn of the key, until it sits for awhile then starts all over again.
Parts that have been replaced are as follows: fuel pump relay, oil pressure sending unit, oil pressure switch, ecm.
FP relay was back-probed with no "2 second" prime, there is power to the relay, resistance on wires from the relay to the ecm were checked, ground wire bypassed to a frame ground with no change, FP/ECM fuse replaced, FP resistance was checked, pigtail over rear axle was checked.....the list goes on.
We are still at a loss for this car behavior. My only though might be the connector at the ecm.......but is there any way to verify if the connector is bad??
We're stumped and could use some fresh ideas.

 

New ECM? ECM initiates 2 sec prime. What about chip

Ground bypassed?


With key off

Disconnect ECM.

Apply 12v to ALDL Terminal "G" pump should run continuously. This is a diagnostic bypass, bypass is defined as a circuit in parallel with other circuits which in this case includes the ECM and Oil Pressure Switch.
Apply 12 volts to pump circuit 465 ECM A-B connector pin A1 pump should run continuously.

Repeat test 2 while checking for intermittent connections in all pump wirng and connectors.

Test for prime, reconnect ECM disconnect pump relay use a test light from pump relay connector terminal "C" to ground.
Turn key on test light should stay on for prime duration.

 

Thanks rgarcia63.....the ecm was replaced. Hoping the new ecm would, as you say, initiate the 2 second prime. It remained the same.
We thought the same about the chip since who it was purchased from had an aftermarket chip in it. We put the original chip back in and the issues remained the same.
In thinking there might be a bad ground the black and white wire off of the FP relay was "cut" into and grounded on the frame.
We tested for the prime duration off of terminal "C" and got zip, zero.

Not sure if we ran to the ALDL ....but I will try that in the AM.

Again thanx for the help.......I'll post the results

 

I assume the ground side of the test light was connected directly to ground and not the ground wire in the Relay connector.

If this isn't a 1227165 ECM then verify which pin on the ECM connector goes to terminal "C" then, use the test light again, but this time at the ECM A-B Connector If you get the prime there then there's a break in the wire before it gets to the relay connector. If not the ECM connector isn't making good contact with the ECM, or that ECM is bad as well. Would be nice if you could put your ECM in another car.

 

Did you check the 3 amp crank signal fuse from the starter to the ECM? May be worth a look. It's located in the fuse block. good luck

 

Crank Fuse is for the Cold Start Injector and Cold Start Switch in pre-'89s,

The fuel pump relay coil itself has no fused circuit and is connected directly to the ECM and engine ground.

A "Hot at all times" 20 amp inline fuse at the Battery supplies 12v to:

1. Fuel (oil pressure) Pump Switch
2. Switch inside the Fuel Pump Relay that feeds the:
   1. MAF Sensor
   2. ECM's internal voltage regulator
   3. Fuel Pump.

Because the relay coil is directly connected to the ECM only it can energize the coil.

FYI
The manual warns against measuring ECM signal resistances, i believe this is because it may damage the ECM.

 

]In the mitchell manual they have the fuse going to the relay coil and the cold start injector. maybe its a miss print I'll check my GM book tonight. I would think if the cold start injector was working it would fire up and then shut off after the fuel was used. just a thought

 

The cold start circuit is powered by the ignition run/start through the crank fuse once the cold start switch times out (warms up) it's switch opens breaking the cold start injector's path to ground. The amount of time the injector is on is temperature dependent. If the fuel pump were powered by this circuit the pump would shut off when the circuit times out.

 

Not the pump,the hold in relay coil, it's 3 amp, not enough to power the pump but will be ample for the relay coil. Your right about the circuit operation but in most cases the ECM doesn't power anything it just provides a ground to complete the circuit.

 

As for the fuse that may be true for later non cold start injector models.
S143 in the diagram is a multiple ground junction on the rear left side of the head.
I know I've posted this image in the past, but couldn't find it.

 

Excellent information guys. Going back a bit..yes the test light was grounded properly. All the fuses were checked and/or changed. Now speaking of fuses, the 30 amp fuse on the fenderwell was originally found to be bad. The fuse was changed and the fuel pump ran the 2 second prime only once. The didn't appear blown but was changed anyway. This scenario was early on in the process and could not be replicated. Still trying to get at the connector with all the time constrants.

We'll keep pluggin' and postin' 'til we get it right..................hate posts that just "end" with no explination.
Again guys, thanx for all the help and input

 

/

 

FINALLY!!!!
Appears the problem has been resolve. Just a brief recap of what has transpired since the last series of posts. The entire fuel pump circuitry was re-checked and was found to be in good working order, the car was even dropped off at our garage for 2 1/2 weeks hoping they could find the problem. So after a new fuel pump....the car came home the same as it left. MY biggest issue has been "something is not giving the pump the "command" to prime".
With that thinking in mind, when the engine has oil pressure a redundant circuit supplies power to the fuel pump. This circuit goes through an oil pressure sensor/sender. Once the engine has oil pressure the fuel pump will get power even is the relay has failed. That being the case....what tells the ECM to supply power through the relay?? Upon substantial research it was mentioned that the ECM requires a "distributor reference pulse" to show that the vehicle is ready to start and will then power the relay. To shorten this up.....once the ICM (ignition control module) was changed the car started on the first turn of the key. Pump primes as it should.
Again, many thanks to all who jumped in to resolve this.

 

Great you got it going.
I think Little Rat actually pointed it out to himself that it was an ignition problem in his first reply.