Damned Fuel Injection

[clint78z]

I had some snags putting in my Accel DFI, with crappy instructions. I got it running well then a series of stupid things just kept getting worse & worse. 2 injectors died, so I got new ones. Then I found the chip tooth on the dizzy reluctor was giving me erratic igntion, so rebuilt dizzy went in. Still bad then after a ton of diagnosing found that the Chev 4 wire Igntion module had 2 plastic pins that must be removed to get a proper ground. Then it ran good for intial tuning, as soon as I try and take the car away from the garage ugh running crappy again. I will not blame the DFI yet, I won't until I know it is that for sure. It sure makes it hard to diagnose with all this new stuff. It started out real good and just seems to go backwards from there.

 

There is no one remotely in my area to come to my rescue, and I can't exactly take it to a GM dealership or nissan. I am waaaaaaaaay past the point of amusement. It's probably something dumb and small but indetectable. I am very good with a multimeter, and wiring diagrams but I think I need a scope. I have been through the system 1000 times can't find anything wrong.

 

So I have some questions I need to be verified.

 

Base timing should be 20 BTDC at idle for an 81zxt, timing varies up to about 40BTDC. Is this right ??

 

I set up the distributor so the rotor is pointing at #1 cylinder at 20BTDC, and used a lockdown adjustment to set timing by moving the reluctor ring on the vacuum advance mechanism. This is known as setting rotor phasing.

 

I used a timing light to verify that the timing mark on the balancer and the screen were the same.

 

It has 6 new injectors, 1 new distributor, 1 new chev 4 wire ignition module,new igntion wire, new MSD blaster 2 coil, new cap, new plugs, a new fuel filter (old one looked good when torn apart).

 

I haven't verified fuel pressure, quite sure it's not a vacuum leak it go a new intake gasket, and leaks before TB don't matter on MAP sensor system.

 

It seems like it is changing timing, the lockdowns for the dizzy seem solid. I have to put a timing light on it and reverify. It gives starter kickback like it is firing at the wrong time. That would be a pain in the ass if I was sold a bummed DFI that couldn't keep proper timing.

 

I think I know this system inside and out, but the car begs to differ. If anyone has any helpful hints I sure could use them.

[clint78z]

Stock distributor with mechanical advance locked out, and vaccuum advance adjustable to set intitial timing. For timing you set the whole map at say 15 then when idling you hookup the timing light and adjust the mark on the balancer to 15 using the modified vacuum advance mechanism. I did this and it was good but seems to have changed since I have driven it. I have to reverify.

[z-ya]

you wrote:

 

It gives starter kickback like it is firing at the wrong time.

 

Check that you have the plug wire connected correctly. I had a similar problem where the book I was using as a reference was inccorrect. The engine would almost start, but would kick back.

 

If this isn't the problem make sure that the timming matches what you have set in the DFI. Does the DFI have a crank timming adjustment? If so, set it to zero. Put a timming light on it while someone else cranks it over. The timming with the light should read 0 degrees. If it doesn't, something is weird with your trigger wheel or something.

 

Question: are you using a crank trigger? If so, why are you using the distributor?.

 

Pete

[Guest Fast Frog]

Clint:

 

The Accel tech that originally installed my DFI sys has helped me out several times! I'll give you his phone # tho I know he's got an email address-but I don't have it. His name is Ron Anderson (970)667-4239. Best time to call is 8-9AM Mtn Std time. Hope this helps.

 

Rick

[Lockjaw]

Do you have an 02 sensor in the system? If so, you can get a rough idea of where your fuel is by the voltage reading it is giving you. .47 volts is approximately stoich, and the higher the voltage, the richer the mixture. You should shoot for high.8's to low.9's and WOT.

 

An egt would be nice, or a wideband even better.

 

Although I am not an expert, I don't like the way you have the timing set for some reason. I agree with 20 degree's at base, and I guess I could find out from Clark what my highest timing is, but I would be shocked if it went as high as 40 degree's. That just seems way to high to me.

[clint78z]

Yes I do have an O2 sensor and display on my laptop. I am aware that above .5v is rich. However if you don't have a good spark to ignite all the mixture, you will get a rich reading as well. Or if the ignition has a miss in it, it will also give rich readings as well.

 

On the open chambered heads like the L6 benifit from more igntion advance than newer cars. Trouble is if you go too much, detonation will occur. Newer chamber design is much better against preignintion happening. The ignition goes 40degrees at 0.5bar and 2400rpm, basically light cruise conditions. Benifits of this are better gas mileage and tip in throttle response.

Once I get to 1bar it is back to 36max.

[SleeperZ]

Originally posted by clint78z:

Yes I do have an O2 sensor and display on my laptop. I am aware that above .5v is rich. However if you don't have a good spark to ignite all the mixture, you will get a rich reading as well. Or if the ignition has a miss in it, it will also give rich readings as well.

I'm not sure if this is true...a misfire will have loads of oxygen in it, and that is all the O2 sensor detects. So it seems to me a misfire will register lean. I had ignition problems (bad wires), and when I'd get on it, I'd see my mixture slam lean - checked fuel pressure and injectors for hours, never found a fuel delivery problem, and it certainly did not smell lean.

[BLKMGK]

Confirmed - a miss or bad ignition comes out lean, there's no missing oxygen in that case which is what an Oxygen Sensor looks for. I've seen this on my W/B. Frankly, after using a W/B I'd never try to tune a car without one - it's awesome!

 

As for timing - on my car, Supra, timing on the OEM box can supposedly goto 50degrees. I've got mine as high as 40 now (much improved MPG!) but it stumbles some. (shrug) The DFI should have a crank timing section and an RPM where it leaves crank condition - make sure that's not too low...

[clint78z]

Thanks I will probably pound my head against the wall a bit more. Trouble is right now I don't trust anything on the car. It is running rich right now, and I am not sure it is that way because the ignition is not doing it's job or I have too much fuel dialed in. I would like to get a scope on the igntion to make sure I am getting proper voltage and the pattern looks good. Do a fuel pressure test to see fuel pump is good. When I am sure all mechanicals are good I will start messing with the programming. Right now there is no TPS sensor yet.

 

I got a map from Tim78zt his car has been dynoed, but it is very rich in the mid rpm to the point were it makes your eyes water . Then once it hits 3 1/2 grand and 2 psi boost it pulls like a freight train. He has a different turbo and intercooler, higher compr pistons. I compensated for the injector and fuel pressure differnce in my maps. I scratch my head why mine is that far out. Since I don't have the TPS yet I can't switch into closed loop, and it doesn't give me that extra shot of fuel on throttle tip in. Mabey I am just being a wuss about pulling extra fuel out, I guess I just keep tack of the plug readings and O2 outputs.

 

Plans are to take it to the dyno once I know everything is tip top

[clint78z]

Yes you are right on the lean reading, wasn't thinking of that correctly. However checking plugs is still important, since one cylinder could be running leaner and cause detonation on that one even though the combined air fuel ratio of all cylinders is correct. Wideband would be nice, where do you usually park your car ?? Anyhow I just got the timing light into town to check timing tonight.

 

Damned laptop battery has kicked the bucket, anyone got a 1/4 mile extension cord ?? Forces of nature stacked against me, most definately !!

 

The DFI you can't set the timing on startup, you are stuck with whatever is built into the Chev igntion module. The DFI only takes control after the engine is spinning over 400rpm. I think 8 degrees is the module setting.

 

Anyhow thanx for the info guys, and setting me straight on the misfire lean reading.

[z-ya]

Clint78z wrote:

 

The DFI you can't set the timing on startup, you are stuck with whatever is built into the Chev igntion module. The DFI only takes control after the engine is spinning over 400rpm. I think 8 degrees is the module setting.

 

If the DFI does not have a crank timing setting, then the timing will be whatever the distributor is set to. The GM HEI module adds minimal delay, so no noticable change in timing will be seen.

 

Another thing that just came to mind: if you are using the distributor, then the DFI can only retard the timing (delay it) with relation to where the timming is via the placement of the distributor. Is this true?

 

Pete

[clint78z]

Well here is how the igntion sytem works, all components of the DFI are almost identical to a Chev 350 TPI computer.

 

The engine cranks over spinning a reluctor in the distributor(dizzy). This creates an AC voltage which goes to an 88 Chev pickup module made for Electronic Spark Timing. The module delays the igntion firing buy a set amount. Once the engine spins over 400rpm from the reference wire on the module, the computer bypasses the module and takes over ignition timing.

 

Setting the dizzy position is done one time, it syncs the timing on the screen to whats actually on the balancer.

Here's a clip from the manual

9)Set timing-When setting the timing on an ACCEL ECU, it is critical to make sure you synchronize the timing between the harmonic balancer and the base timing matrix. If this is not done, the timing program that you implement may not be accurate. To synchronize the timing, first enter the ignition menu and save the current timing map in a subfile by executing "save ignition map in a file" routine. This will allow you to revert back to the original timing program without reprogramming the whole ECU. Once the map is saved and titled, return to the timing matrix and press the "E" key to place CALMAP in edit mode. Since the timing map interpolates values from one cell to another, it is essential to make a set timing map of one value. It is usually best to use a value of 6 degrees for Chevy's and 10 degrees for Fords.

 

What ever value you use, convert the whole matrix to that number. You will now have a map with all the same numbers. Start the engine and let it idle. With your timing light hooked up, physically adjust the distributor until the value on the dampner reads the same as the value in the boxed area below the timing matrix. Please note that during this initial set up procedure, we have already zeroed the idle spark function. If you are just going to check the timing for sync on a vehicle and not executing the complete base set up, make sure you raise the TPS to over 1.5% to disable the idle spark function. It is easier to disable it this way in lieu of erasing an established idle spark program. For the initial set up you should choose to zero the idle spark due to the fact that it has not been established as to what degree it will be needed. When the timing procedure is completed, return the TPS to a setting of 0-.5% and re-enter the already saved timing map by executing the "Program the ignition from a file" routine.

 

The computer controlls the firing event of the coil, it fires whatever degree BTDC you type into the igntion map.

[clint78z]

I am pleased to report the car runs like a champ now. It was the plastic injector base that was cracked and the one fuel injector was not sealing properly. It's a friggin madman on the freeway, I had to tell my roomate to slow down he was doing like 90mph in a blink of an eye.

 

I am very pleased with low rpm response with the T3/T04E-57mm and stage III but .63 a/r. Things are still limited to 4400rpm and 7psi boost right now for break in. Thanx to everyone for all there help. It is done just in time to park it for the winter