Thruster DFI problem

[mikey]

H Guys

After starting and running the engine a couple of times, it wont start at all now. Big spark at the plugs and seems to be getting fuel. The symptoms sound a bit like an engine with the timing out too far when it wont start. When it was running the software was matching the timing on the pulley.


Second time this has happened. Last time I took the distributor out and re – timed it and it fired up.



Have you any ideas, particularly on how to check the distributor as the troubleshooting charts don’t seem to zoom in on that sort of problem when its been running and then with no changes wont start. It’s a new battery and a big one so I am getting plenty of voltage.



Engine is a 415 Chevy Motown and I have the Accel Dual Sync. I am running on returnless setting as although I have a return to the tank I have no vacuum to the regulator (is this right)



Your thoughts would be appreciated.

Regards
Mike

[vector1]

find the cranking cell on your a/f table, timing table, and ve table. these values will tell you prob why it won't start.

my v/e table was way off on cranking and i had to drop it to .431 and .426. would foul the plugs real easy. my engine is about the same size as yours so this might work. my cranking cells are 200 rpm, .26 and -.56 on the map values.

if your plugs are fouling the time it took you to remove the dist. and retime your plugs could have allowed the plugs to dry.

if you floor the accel pedal it should turn the injectors off when you crank the engine by the way, if your plugs are fouling.

on the dual sync dist., you phased the cam light, dist light, and rotor?

i don't know if your fuel return setup would fool the dfi, but you should be able to run a vacuum hose from the throttle body to the regulator. the fuel pressure will then be adjusted by manifold vacuum and read lower by about 5 lbs, but this is correct. and switch to return on the dfi. if i remember correctly, the fuel pressure is set without engine running.

did you force the timing to check if the crank was matched with what the dfi was using? if these are different then you will have to use crankoffset to match the numbers.

don't worry, i went through the same thing you are. you're going to learn a lot.

you're not getting any trouble codes?

[mikey]

Originally Posted by vector1

find the cranking cell on your a/f table, timing table, and ve table. these values will tell you prob why it won't start.

my v/e table was way off on cranking and i had to drop it to .431 and .426. would foul the plugs real easy. my engine is about the same size as yours so this might work. my cranking cells are 200 rpm, .26 and -.56 on the map values.

if your plugs are fouling the time it took you to remove the dist. and retime your plugs could have allowed the plugs to dry.

if you floor the accel pedal it should turn the injectors off when you crank the engine by the way, if your plugs are fouling.

on the dual sync dist., you phased the cam light, dist light, and rotor?

i don't know if your fuel return setup would fool the dfi, but you should be able to run a vacuum hose from the throttle body to the regulator. the fuel pressure will then be adjusted by manifold vacuum and read lower by about 5 lbs, but this is correct. and switch to return on the dfi. if i remember correctly, the fuel pressure is set without engine running.

did you force the timing to check if the crank was matched with what the dfi was using? if these are different then you will have to use crankoffset to match the numbers.

don't worry, i went through the same thing you are. you're going to learn a lot.

you're not getting any trouble codes?

Thanks for your help. In the end, there was massive overfuelling at start up and warm up enrichment - it is a global calibration accel did for me. I zeroed everything and started again. Started first time and at least can look forward to tuning it. Just out of interest do you know if there is a lambda gauge that will fit with the accel sensor box that you dont need to buy all the gubbins with.

All the best

Mike

[vector1]

man, i can't understand you, i've been away from the motherland too long!

there is an accel datalogger that is real helpful that i use. opens up a whole new can of worms but once you get the hang of it you can tune yourself. otherwise you go to a dyno and use their o2 sensors. one trip to the dyno almost pays for the datalogger.

what's a gubbin?

[mikey]

Originally Posted by vector1

man, i can't understand you, i've been away from the motherland too long!

there is an accel datalogger that is real helpful that i use. opens up a whole new can of worms but once you get the hang of it you can tune yourself. otherwise you go to a dyno and use their o2 sensors. one trip to the dyno almost pays for the datalogger.

what's a gubbin?

Sorry about the slang - gubbins is the accessories or bits and pieces needed with it. In the case of the gauge or data logger, it would be the lamda sensor probe and wiring. As I have the accel black box that came with the thruster kit all I would need I guess is a harness if there is a seperate feed point from the box. I will contact accel.

I have an Innovate kit which which i used for tuning the Barry Grant speed demon, but I will try the accel one integral with the thruster software.

The only reason for the gauge is to use it for keeping an eye on the A/F readings in open loop to fine tune the VE before I set to closed loop and as a safeguard in closed loop once I have done this I guess.

I suppose the response will be to use the calibrate function to get VE points and smooth the graph - is this the way you did it initially.

There are not many rolling roads that can take the power over here and less people familiar with tuning these set ups unlike the speed shops over there. There are a few dyno rigs, but it is a hasstle to pull out the engine and I wanted to have a go myself. I am used to drilling out air bleeds and modifying carbs but this is a whole new ball game.

Thanks for all your help.

Regards
Mike

[vector1]

if there is a datalogger for use with the thruster, that is the way to go.

the datalogger will have a seperate program for your computer called accel dfi datamap and you download off of the datalogger in the car to this program, then you can export this file to calmap and under datalogging-fuel you can bring it up and run it on your ve table that is in the car and it will show which cell your in and how much fuel the thruster is pulling or adding which is really a multiplier that you multiply the cell by.

once your get your ve table close you can look at th fuel and spark tables and treat it like you would a carb setup, putting a/f ratio where you want it and likewise with spark.

after you mess with the datalogger you will get a feel of what cell the car operates at what engine loads like part throttle cruise, no load, etc., and you can move the spark and a/f where you want.

some of the other efi makers have better instructions if you can find and use them on setting things up.

how to tune & modify engine management systems by jeff hartman has some good info under the ems tuning 101 chapter. this has been the best book i have found although the info is still limited.

i also looked at a lot of different spark and a/f tables to get an idea of what others were doing.

http://www.megamanual.com/mtabcon.htm

i am not sure how the thruster is set up so the above info regarding the datalogger might be unuseable.

here is where i purchase my stuff, reasonable american dollars located in central u.s.

http://www.efisupply.com/store.htm

hth

i have found smoothing the ve table really does no good because the engine wants what it wants at certain points no matter what. you can smooth outside where it operates, like the cells the engine will never see. although the book i mentioned above says to string the operating cells together and smooth outside of those and you will be close.

with the datalogger you can tune in closed loop, although i have seen reference to tuning in open loop. the one time i took my car to the dyno the guy turned off closed loop to tune the ve cells.

another thing with the o2 sensor, put it in a collector if you can, but make sure there are no slip fit connections upstream, any amount of leak will throw it off i have found. also you do not want any leaks at the heads you probably know.

i had to put the sensor in a primary pipe and the reading jumps around more than a collector does.