80Sierra

I'm right out of ideas here guys. My TPI has been running stupidly rich since day one, and I can't find out why.

I've got a set of orange topped 19 lb Ford injectors in the truck, with a stock TPI fuel pump and stock fuel pressure regulator. I had been assuming that most of my problem was the injectors leaking when the truck was off, as my fuel pressure rapidly falls after priming the system. I took the intake apart, and checked the injectors to see which ones were dribbling, and while the tips on one or two of them got moist after a few seconds, none dribbled anything. I must be loosing pressure back into the tank through the check valve in the fuel pump.

I also figured that I'd try turning the injector constant way up in the prom. I programmed it to think it had 24 lb injectors, and while that stopped it from smoking, it still runs stupidly rich. Lots of backfiring, and gas fouled plugs.

What in the world is possessing the ECM to pour so much fuel into my engine?!

RednGold86Z

iTrader: (1)

Could be a few things.

Does the vacuum reference tube have fuel in it? Is it connected properly?

Do you have a scan tool? Read your MAP voltage at idle (assuming you're using MAP). If it's above 4V, you have a MAP sensor problem.

Also, scan for the CTS (coolant temperature sensor) reading. Check the resistance of the sensor vs temperature. Check it according to spec (found in most repair manuals).

If MAF, try disconnecting the MAF to see if it improves.

It might be in limp-home mode. Do you have a check engine light installed?

Can you read any error codes from the ECU?

Do you have a cold start injector on the car? Try disconnecting it after it's started to see if it clears up.

Also, if you have fouled plugs, it may be hard to detect if you've fixed any of the problems until they are cleaned or replaced.

If all else fails, try borrowing a good ECU.

80Sierra

No fuel in the regulator, and yes, it does regulate the fuel pressure correctly. I went ahead and ran the fuel pump for about five minutes with the engine off and the rails of the engine. Again, the tips of 2 or 3 injectors got moist, but none of them dripped. Cold start injector included.

I will need to get my laptop rigged up to read the `7730 ECM somehow. I have no way of getting the software onto the laptop, cause I have no CD-ROM, or any networking abilities, and the floppy drive is to small to hold Datamaster.

I did however check the CTS resistance, and it was within spec for the temp that the engine is at. That was one of the first things I checked. The MAT, and TPS are also within spec. Also tried both my `7730 ECMs, with both operating the same way.

I do have a check engine light, and it isn't running in limp mode. It was at first, until I was able to properly calculate the checksum to get it to work properly.

I had also totally forgot that a guy can check codes without a scanner, but since I took the battery cable off while taking the intake apart, it will have reset the ECM.

I plan to get some new AC-Delco plugs into the engine, but I'm not sure I want to install them just to foul them out right away prior to fixing the rich problem.

RednGold86Z

iTrader: (1)

Wait a second - you're using a cold start injector with 730?? Hope it's disconnected.

Moist tips aren't good, but hopefully not the cause of extreme richness to the point of smoke.

Either something is telling the computer to inject longer (i.e. MAP signal is high, CTS is high ohm = low temp, or O2 low with high BLM (but shouldn't affect cold start, so likely not that)), or something else is bad - like EGR stuck open, or possibly a bad block off plate.

You should disable checksum in the bin while you're at it. And VATS, of course (assume that's already done).

Is the engine basically stock? Or is a menacing cam in there? If cammed, it's gonna take a LOT of VE work to get it to stop being so rich down low.

80Sierra

Yep, the Cold Start injector is simply acting as a blockoff plate. It isn't hooked up. The TPI setup used to be MAF, but I converted to Speed Density before I did anything.

I know that moist tips is a bad thing, and I've already got a fresh set of injectors coming to replace them. But, fortunately they are not the cause of the fuel pressure loss. That has to be in the fuel tank.

Fortunately, I was able to find myself a laptop to use as a scanner, I'll have it for this afternoon, so I can finally stop stabbing in the dark, and have a look at what the ECM is seeing

I do have the EGR valve installed yet, but it isn't hooked up to a vaccum source. So like the Cold Start Injector, it is just acting as a blockoff plate.

Checksum has been removed already, and yes, it does have a mild camshaft that is hardly suited for EFI. I am expecting a rich idle, but I do have a pretty good idea of what its going to take to get it to lean out at an idle. Either by forcing open loop at an idle, or by changing the idle target A/F ratio. My biggest thing was that I've been flying blind up till this afternoon, so I can finally get something done now!

80Sierra

Well, I got the laptop hooked up and caught a bit of datalogging. However, while I thought It'd help, its a whole lot to digest. I've got a lot of work ahead of me, LOL