lakeffect2

I'm having some "no start" issues on TPI swap. Got spark, got Noid signal at injectors, but fuel pressure drops immediately after the Fuel relay times out.
I'd like to keep it on a fuel seconds longer due to my long crank times, but can't find where thew relay time during cranking is found. I'm using Tunerpro, latest version.

SInce the pressure is dropping after the relay cuts out, it would seem the drop is caused by the continued opening of the injectors while still cranking. Oddly I don't seem to have drenched plugs. They still seem dry and were just bench tested to check for being hung open.

I've been thinking of increasing "cranking pulse width" due to the seemingly dry plugs. Maybe there isn't enough fuel because it is a 406 with 32lb/hr injectors, compared to stock a 305/350 with 19/24lb/hr?

Cambridge205

Hopefully you thought of this already but maybe you have a bad fuel pressure regulator?

How much pressure do you have when the pump is running? Did you replace the pump when you did the swap? TPI pumps pump more than the TBI ones do. I don't think this has anything to do with the injectors. Injectors don't normally stay open unless they are old and broken.

Apeiron

The fuel pump is turned on during cranking as soon as the ECM starts receiving reference pulses from the distributor, and for 2 seconds after the last pulse is seen. You don't need to change its behavior.

lakeffect2

To Cambridge 205: Thanks for responding. Pressure pumps up to 42lbs, but drops after relay cuts out. Regulator has been tested by clamping off return line. Line pressure drops with continued cranking, but holds when I stop


Apeiron: Since it's cranking, shouldn't the reference pulse still be available to be seen by the ECM throughout cranking? The relay clicks out after two or three seconds even though I'm still cranking. Maybe it's not seeing any pulse?

I'm using a "730" ECM. Should I be seeing a pulse on the purple/white wire? (circuit 430) This is the second brand new module, new distributor, in the car, and still no joy.

Apeiron

The distributor should be sending pulses, and the fuel pump should be on the whole time during cranking

lakeffect2

Sounds like it the next thing needing verification! My impression is that the pump cuts out, as I'm hearing hear the relay click, and therefore it does not remain on.

I'll have to prove or disprove that point. Any thoughts?

lakeffect2

15 minutes later; I have a "Painless Wiring" harness, long enough to hold the relay in my hand during cranking. Relay absolutely clicks about two seconds into cranking, and does not reactivate while cranking continues.

moments ago, I progressively put a NOID light into the injector harness to check for pulse for cyls 1 and 3, 2 and 4. Last week I was fine, both banks, this week I got nothing either bank. (verified via 9 volt battery that NOid light was working.)

lakeffect2

I'm running a Prominator in a 730 ECM. I just switched to a different program number and the noid light worked again, although it did not fire up. Wierd!

Apeiron

You won't get injector pulses without reference pulses from the distributor, either.

Sounds like you have some ECM problems.

Egg83

Well this may be totally unrelated but nonetheless helpful. You stated that this is a TPI swap. Do you have an oil pressure switch hooked up? Im not talking about the sending unit for the gauge but the switch. And if so is this switch good? The ECM will automatically prime the system when the key is turned resulting in pressure as you described. But for the fuel pump to run when cranking/ running you need oil pressure to satisfy the switch. Just a thought. Id look there before you start replacing anymore parts. -Bob

Toehead

Bob, that is only true if the relay is bad or the computer is failing to turn the relay on.

The oil pressure switch is a failsafe for the relay.

MattODoom

iTrader: (1)

Yeah, as I understand it, the switch is not a necessity for the pump to run. Its just a backup so if the relay dies, the fuel pump will still come on when the motor builds oil pressure. This will create a long crank time but at least allows the car to run with a bad relay.

Egg83

Toehead/ MattODoom, he stated earlier in the post that the fuel pressure would be normal then drop after the relay timed out. Then, while cranking it would drop all together. He stated that the relay was clicking so that leads me to believe the relay is switching power to the fuel pump for the initial prime. But for the fuel pump to run continuously the ECM has to see oil pressure at the switch to let the relay switch power to the fuel pump. If that weren't the case when we all sit in our cars with the key in ACC the pump would run forever.
When I was younger, I converted my car from 2.8 to a carbed 355 and wanted to keep the factory fuel pump. I stepped the pressure down with a 3-port FPR. Anyhoo, it took me sometime to figure out why the pump wouldn't run for me with the 2.8 MPFI computer and wiring removed. I found that the ECM controls the fuel pump from the oil pressure switch. I ended up making my own set of relays with a oil pressure switch.
IMHO it sounds to me here like his relay is switching for the initial prime but not running after. -Bob

Apeiron

No it doesn't. The ECM will control the fuel pump perfectly happily without an oil pressure switch even installed. The oil pressure switch isn't even an input to the ECM. It's only a backup for the fuel pump relay. The reason the fuel pump doesn't run while the key is on is because the ECM knows the engine isn't running because it sees no reference pulses from the distributor.

Fast355

iTrader: (2)

This whole problem sounds like a VATS issue. If its enabled in the calibration and the ECM does not see a signal from the VATS module, the ECM will not fuel the engine.

MattODoom

iTrader: (1)

Correct! Sorry Egg83, but the pressure switch is just a redundancy.

lakeffect2

I believe Ii've accounted for VATS with "switch 16 box 4" in the mask by making sure the box does not have a check mark. My understanding of VATS (please correct my error) is that it cuts out the injector pulses. I'm clearly seeing the NOID light firing off. So my logic is VATS is not an issue otherwise the noid light would not be reacting, although I thank you for reminding me.


Oddly, or at least a clue, is that shooting starting fluid down it's throat gives me some cylinder firings, so this seems to be (maybe not so clearly) a fuel delivery related issue. There is 42lbs at the rail and noids lights saying the injectors are firing.

I'm at work at the moment and don't have access to to TunerPro files other than to tell you I've been adding 10% more fuel in the "cranking pulse vs temp" section. Should I be making an entry elsewhere?

\
Many thanks for all your kind efforts to help me!

Egg83

Hmm sorry for the mis-information guys/ gals. I was under the impression that the ECM controlled the fuel pump other than during the priming state. So is the 'tach' the signal that controls the fuel pump?
Just to further clarify so you don't think im bs'ing you. I ran 12v ign to the switch and made a relay control the fuel pump via oil pressure so I didnt have to rig it with a toggle switch. -Bob

Apeiron

It's not exactly the tach signal, it's the reference pulse signal from the ignition module. The tach is driven directly off the coil primary. When you put a non-computer distributor in, the ECM stopped getting reference pulses, so you needed an oil pressure switch.

Egg83

Ok good to know. Thanks for explaining that. I learn something new everyday here. -Bob