Injector Characteristics

[clintb00]

I need some help with my injector characteristics settings. Some backgroud info: MS II V3.0 v2.886 1989 Ford Mustang 306 w/ HCI 24lb ford injectors.

I was able to start the car and get it to stumble, backfire, pop and then it died. I reviewed all the settings and everything seemed in order. I initially had my injector open time @ 1ms, battery volatge correction @ 0.2 ms/v, PWM current limit 100%, PWM time threshold (ms) 25.4 and Injector PWM period to 66us.

I changed the injector open time to 2ms and the car ran a little longer, still backfired and popped and died. I bumped it up to 4ms and the car ran decent but would only idle down to ~3000 rpm this time; however, the car would run without backfire or popping and would actually rev. I kept on changing the injector open time by 0.5ms at a time and the engine idle speed would come down. I got up around 10ms when the engine would finally idle around 1000 rpms. This doesn't seem right to me. Any ideas?

[Heribert]

I think your initial inj settinings were about right. Adding opening time to 10 ms is totally wrong.
My guess is that your VE map is way wrong, your req fuel is off and/or your number of squirts is wrong.
Get hold of a realistic VE MAP, calculate req fuel and make sure to start with 2 squirts alternating or one squirt sim.

Heribert

[clintb00]

My required fuel, according to the calculator on Megatune, was 16.7 ms. I have the number of squirts @ 2 alternating.

[john.p.clegg]

Clint

I wouldn't worry too much about your calculated fuel,mine was way out,just alter your VE number till you get a good tickover,then alter your RF so that you end up with around 30 as your VE at tickover..

John

[clintb00]

Thanks John, I'll give that a try once I get home.

Clint

[clintb00]

Well, I think I figured out what was going on... I changed all my injector settings back to "normal" i.e. 1ms open time and engine imidiately died. After some head scratching, I hooked up a fuel pressure gage to discover that my fuel pressure would only build to ~ 15psi and then quickly bleed down to zero. Even with engine running, pressure would not climb past 15 or so psi. I took apart the FPR and everything looked good there, all the fuel lines looked good and the fuel filter was good. It looks like I'm going to order a new fuel pump and go from there. Thoughts?

[kjones6039]

It sounds like a new pump may well be in order.

question though......

Are these Hi or Lo Z injectors?

Ken

[trakkies]

Well, I think I figured out what was going on... I changed all my injector settings back to "normal" i.e. 1ms open time and engine imidiately died. After some head scratching, I hooked up a fuel pressure gage to discover that my fuel pressure would only build to ~ 15psi and then quickly bleed down to zero. Even with engine running, pressure would not climb past 15 or so psi. I took apart the FPR and everything looked good there, all the fuel lines looked good and the fuel filter was good. It looks like I'm going to order a new fuel pump and go from there. Thoughts?

Before you buy a new pump, check it's getting the volts it should. The relay could have dirty contacts, or a poor connection somewhere.

[MustangSix]

Verify the FPR is working by clamping off the return and checking pressure again. If the pump is working properly it should build to 55-65 psi very quickly. If it does, then the FPR is suspect.

[clintb00]

Ken, I believe these are high impedance injectors 11-14ohm but not 100% sure... I'll check the resistance on a few and report back...

Trakkies, I am getting voltage to the pump. The pump will power on and pressure up to 15 psi then it will bleed down.

MustangSix, I planned to do this, building up head pressure on the pump, and check pressure before the FPR via the schrader valve port. I have a Mallory FPR which is serviceable unlike my original BBK unit which grenaded after 3 months, POS. The diaphragm looked good and I cleaned all the ports with a little brake clean for good measure.

Thanks for all the responses guys… keep them coming and I’ll post my findings soon! Thanks,

Clint

[EWflyer]

I've recently been having a fuel pump problem that sound similar to yours: builds pressure only to lose it again. It appears now that my problem is due to trapped air in the fuel system. Just like your situation my pump checked out healthy (getting good current, amp-draw is normal).

Apparently even a little trapped air can cause pump problems. I started off with the fuel pump mounted horizontally which caused huge problems, lot's of pressure fluctuations. A week ago I re-mounted it at about a 45 degree angle, now it runs better (for a while) but the problem still isn't completely solved because after running well at normal pressure, regulated to 42 PSI, it will suddenly drop to 0 PSI even though the pump is still spinning (you can hear it). I'm going to redesign and reinstall my whole fuel system so it can purge air completely. I'm currently gathering info on how I should reconfigure the system.

So I've got more work to do. I had a feeling I hadn't thought out my fuel system design well enough, it was more of a "put it together quick and see if it'll work" sort of job.

Good luck getting your pump sorted, I'll be interested to read about the fix.

[clintb00]

Good news, bad news...

Bad news first: There was lots of corroded parts when I removed the pump assembly. I has less than 1/4 tank of fuel in the car for the past couple of years and never drained it out. The tank, pump, pump hanger and sending unit are starting to rust. I pulled everything out of the tank and pressure washed the inside as best as I could. I used a some brake clean and a blow gun to help the water evaporate. The sending unit doesn't look that bad, some rust specs but nothing that can't be cleaned up without some elbow grease. The pump hanger was a little worse, but still probably salvageable. The pump looked bad but started to clean up nicely. The fuel strainer (sock) was trashed and was falling apart. The rubber line from the pump to the pickup line (hard line) was split and coming apart in several other places. I think I might be able to salvage the majority of these pieces; however I do need a new check valve (little orangish red rubber nipple) for the return line on the pickup assembly, and new mounting gaskets for the fuel pump (pickup) assembly and sending unit.

Good new: well... I'm hoping everything will clean up nicely and I'll be able to use it and not have to buy too many new parts. I'll pickup a new fuel strainer and some new fuel line (and a couple duck bill clips that always break when I try to take them off) and bring the system back to life. I am 99.9% sure this will solve all my fuel pressure problems, which in turn should solve my injector characteristics settings dilemma.

Lesson Learned: Even if you think you will get a chance to work on your project car in a couple of months or so, go ahead and drain the tank. My couple of months turned into starting it once a year ago and now look at me...

Help: does anyone know where I can find the sending unit and fuel pickup mounting gaskets (without having to buy the entire assemblies)? What about that little check valve piece?

Thanks again guys, I'll keep you posted as my progress (hopefully not regression) continues.

Clint

[trakkies]

Some say it's better to fill a tank fully when storing a car.

[MustangSix]

Hopefully none of that crud made it to the injectors. If so, you could still get a lot of inconsistent results. I recommend you pull the injectors for a good cleaning as well.

As far as the sending unit gasket, you should be able to get that at any dealer or from www.npdlink.com.

[clintb00]

I found a gasket and new soft hose for the in tank fuel pump, cleaned everything up as good as I could and put it all back together. Thanks for the advice Mustangsix, I will pull the fuel rail and injectors and give them a good cleaning. I should have this thing up and running by Tuesday... I wont be able to get to much work done with football on the tube. Thanks again for all the replies.

[kjones6039]

Some say it's better to fill a tank fully when storing a car.

I couldn't agree more! No room for condensation to form, IMHO............
It has always been my understanding that the tank should be stored full.

Ken

[trakkies]

I found a gasket and new soft hose for the in tank fuel pump, cleaned everything up as good as I could and put it all back together. Thanks for the advice Mustangsix, I will pull the fuel rail and injectors and give them a good cleaning. I should have this thing up and running by Tuesday... I wont be able to get to much work done with football on the tube. Thanks again for all the replies.

There should be a very fine filter protecting the injectors from crud. The only reason they need cleaning is due to varnish build up from the petrol itself. If there isn't such a filter, fit one ASAP. ;-)