Amp drop when starting - kills injectors

[Ben M]

Race car with 2.5 liter engine, electronic fuel injection. When I engage the starter, it draws the amps below 10, the fuel injectors require 10.5 amps. I installed a larger battery with 800 cranking amps, it still drew down the amps into the low 9's. Any suggestions would be appreciated.....Thanks! Ben

[cmonref]

Are you saying that the injectors do not inject fuel during the start cycle? But they still draw 10.5A while not injecting? Has the engine run in its current configuration?

There are other reasons why the fuel injectors will not inject fuel. If the FI is set with a too-high RPM during starting, the FI does not recognize that starting is underway and keeps the injector circuits off.

A power wire that is too small would result in greatly lowered voltage to both starter and injectors.

Fuel injectors work on voltage, i.e., they work correctly down to some low voltage level. I've seen readings that 4V thru 7V are necessary to operate the injector circuits. What voltage do the injectors see during starting?

[356RS]

Ben, you mean Volts, not Amps, Right?

[Ben M]

Ooops, yes volts not amps.

The electronic injection system is a Electromotive's WinTEC-3 system, according to Clewett Engineering the injectors require a minimum of 10.5 volts to respond properly. When I monitor the system on a laptop, the volts drop into the high 8's or low 9's when the starter in engaged. The low voltage is apparently not enough to fire the injectors. Still searching to see if anyone else has hit this problem.

Thanks again for any thoughts.

[Ben M]

cmonref

The fuel injectors are not injecting fuel during the start cycle.
The engine has run in its configuration, but always been really tough to start.
It will start relatively easy when push started.
I think the started is drawing too many volts, so the injectors are not receiving enough volts.
Not sure how to set the volts for the injectors??
Power wire...excellent, I'll check that.
Not sure what the injectors actually see, I'm watching a volt reading on the main screen.

Thanks, Ben

[Mahler9th]

Some of the old Haltech EFI computers have issues like this. Mine does. The way mine works is that it runs the fuel pump for a few seconds, and if it does not see any tach signal/rpms, the pump relay times out. Repeated attempts to start the engine can drop the battery voltage so far that the injectors won't fire.

So what I/we do, is tap into the injector harness, ground side. In my application, the injectors fire in pairs, so I have as many as three grounds to work with.

I have inexpensive radio shack momentary switches in my dash (3, although 1-2 would probably do), and I can ground 1, 2 or all three injector pairs as part of my starting sequence.

So once I hit my main power switch, I can push 1, 2 or all three momentary switches to squirt a little fuel in the cylinders, and the car starts right up. I have to do so within a few seconds of turning on the power, because if I wait too long, Mr. Haltech turns off the fuel pump.

[Tippy]

High CR with a stock starter would draw some juice.

A high-torque gear reduction starter would dree up the power.

[Mahler9th]

To prevent the possibility of grounding/firing the injectors inadvertently, I have a simple toggle switch that is in the path to ground for all three momentary switches.

So my sequence is: "injector" switch "on," fuel pump #2 switch on, main power switch on (which turns on Haltech and fuel pump 1 on), then depress 1, 2 or all 3 momentary switches to squirt some fuel into the cylinders, then starter pushbutton.

With this set up I can use a really small Ah/CCA battery.

Picture of dash shows the three red radio shack momentary switches.

A number of us use this type of solution. Perhaps something similar can work for you.

[T77911S]

no electrical/electronic device (load) draws volts.
loads draw or require current.
starters and solenoids require a lot of current and need very low resistive circuits.

voltage drop is due to 2 things, resistance or bad battery. really 3, the 3rd would be a load so hi that the battery cant deliver the current but pulling 800 amps would melt wires.

resistance causes a voltage drop ACROSS the resistance.
resistance also reduces current flow.
think of current kind of as power to run the load. (power actually equals volts x current but the voltage should always be the same so current is the variable).

so lets go back and look at resistance since you have a new battery.
first I would start with CLEANING all major power connections, that means GROUNDS too. these are very often over looked. make sure you have a very good connection for ground from the body to the engine.

next I would look at crimps since things have probably been spliced into the wiring,.
crimps alone really suck in my opinion. (use to do auto electric work so I have dealt with my share of them). they may look good but a good tug on them can show a bad connection. this bad connection equals resistance. resistance = voltage drop.
I like to solder and crimp connections.

I would put a MM on the battery and look at the voltage there while cranking. I am betting that voltage is good and that your problem is probably a crimped connector.
the ECU is asking for more current, there is resistance thus the increase in current thru a hi resistance = voltage drop.

get a test light. probe the connectors while cranking.
if you use a MM, measure al voltages referenced to ground.
if you DO find a bad connector, measure voltage across the connector. you will probably see about 2-3 volts across it. don't do this to find the bad connector, only after.

[Ben M]

Grounding the injectors in the starting sequence makes sense. I'll add three momentary switches into the dash and use them with the starting sequence. Also double check all the ground connections and connectors for lose connections.
Thank Guys!

[prschmn]

All the adding switches etc. is more likely than not just working around inadequate wiring.
Either the wire gauge is too small or there are poor joints somewhere.
Remember that lower voltage electrical systems require much larger gauges than higher voltage stuff.

[T77911S]

I hope you mean larger gauge as in 24 is larger than 18, although wire size is opposite.

gauge or wire size is determined by load. (current). and length.
fuse amperage is determined by wire size.

take your house for example.
a 15 amp breaker is for 14g wire, a 20 amp is for 12g.


if you put a 20amp breaker on 14g wire, the wire can over heat and catch fire before the breaker trips.


you start adding switches in SERIES with the signal or ground back to the ECU you add potential for failure.
running a wire in parallel to switch to prime the engine for starting is ok.

I buy the bare terminals so I can crimp and solder them, then I slide heat shrink of it.

[Mahler9th]

My wiring is not inadequate. It is all custom and time-tested.

My engine uses Bosch injectors that were stock on 944 turbos.

My Haltech EFI is vintage-- circa y2k.

It worked okay without the intervention with a really big battery, but I wanted to use a really small battery. I use a 13 pound Interstate motorcycle battery.

I have a few friends with the same vintage Haltech and they have implemented the same scheme.

I have had mine in place for 10+ years. No issues.

It is possible that my engine builder got the idea for this approach directly from Haltech.

I tend not to have electrical problems with my race car... I am pretty good at designing and implementing wiring schemes. I spent a six-month stint during a break from college (I studied electrical engineering) helping to design wiring harnesses for a GE digital x-ray system.

In my case, the switches are not in series with the EFI-injector grounds. The scheme simply enables me to have a momentary path to ground for injector pairs, which when the EFI system is on and the EFI-controlled FP is running, squirts a little fuel into the cylinders.

I don't know whether this kind of approach will work for the OP's issue, so I provide this perspective as food for thought.

[T77911S]

I hope you don't think I was implying you have a bad setup.
i actually did not read much of your post.
I only make suggestions and that's based on 25+yrs as an electronics tech for the FAA fixing the stuff engineers design and a yr as an auto electric tech fixing the crap people did to their cars.
big problems, aftermarket alarms and BAD installs.

I like things simple and reliable,
that's why I am such a big fan of CIS, no electronic crap to go bad.

[Mahler9th]

No worries.

Hopefully the OP has some food for thought.

A further suggestion would be to engage the EFI MFR with additional perspective from this and other resources and considerations to see if they have helpful thoughts.

For my situation, the system I have implemented works great. Flawless actually.

My friend/engine builder is highly experienced, well regarded and an expert, and worked with Bruce Anderson and Jerry Woods back in the day. He also raced professionally in IMSA.

When he has implemented this approach in his own cars and those of other friends, he did not include the toggle switch. I put it in so that you have to deliberately allow/disallow the momentary switches to provide a path to ground.

Race cars can have different needs than street cars.

As an aside, I have a lot of friends that tried and abandoned Electromotive EFI and ignition products of various vintages. But I also know a lot of people that have had great success with their various products.

Our "herd" is fond of Haltech and MSD.

Another nearby race engine builder has a lot of Motec EFI customers. He also works on older tech tech like 935 and 962 engines. He is extremely experienced and expert.

Lots of ways to skin a cat.

[T77911S]

who is the IMSA guy.

danny smith that raced and won the GTU(?) division many times lives(d) around the corner from me.
he raced a rx7.

I have considered going EFI on my 930. I am EXTREMELY picky when it comes to cars and how they run. I can hear small differences in how my car runs and it bugs me. no one else hears them because they don't drive it all the time.
money is one if the things stopping me.

funny, I got rid of all my electronics and my coil died on my about 2 weeks ago. fortunately I keep another ready to go. (MSD) they are only $50.

[Mahler9th]

We can discuss offline-- you can send me a PM.

But just as a quick aside, the conventional MSD Blaster coils do not like to be run upside down. So if you are using one of these, and it is mounted with the terminals facing down, you might remount with the terminals facing up. They do have a version that is potted and more easily able to be mounted in any orientation.

I use Blaster 2's as do many of my friends. Two in my case.

I have used these coils for 18 years. I carry spares. The only failure I have had was in my first year with the car, in the first lap of a race.

I learned about this from a friend, a Kiwi who at the time was working for TRG. He had extensive pro and amateur experience. His brother was also involved with racing. F1 team BAR Honda. Back in the day.

Anyway, we can take our further discussions to a different thread or PM. Hopefully the OP here will solve his issue(s), and we will have helped. And he will close the loop for posterity in these Forums.

[Charles Freeborn]

Running a MSD? They're power hogs too.

[r_towle]

consider two batteries (its a race car)
One to run it, one larger one, on a cart, to start it.

there are some very heavy duty DC plugs out there if you look around , super cables are tacky if you can do it right...

rich

[T77911S]

I like the way the MSD is wired.
it has a direct connection to 12v for the spark side of the circuit unlike the bosch which gets its power thru the ign switch.
it also has an LED on it that flashes with input, just came in handy when coil went bad.
also has adjustable rev limiter. that let me remove the factory one under the seat. point of failure.

I flipped the coil a long time ago., had clewett make me a special coil wire long enough to reach.
fits nicely under the IC.
I also can unplug the MSD and plug in the bosch unit if needed.
I had the spare coil wired to the factory wiring harness but did not have the bosch unit with me so I had to swap wires.