What would cause the Voltage to the Primary injectors to fluxuate?
 

I am getting a bucking around 2800 rpm.

Well, I hooked a volt meter to my Front Secondary (3H) wire on my ecu and drove around. The voltage moved from 13.64-13.67. Pretty steady. Then I hooked the volt meter to the Front Primary (3E) and the voltage starts at 13.25 (idle) and will drop as low as 11.**. The closer I get to 2800rpm the voltage drops lower. When it bucks the worst is when it hits the 11.** volts. What controls the vols to the Injectors?

3C Rear Primary Voltage drops 13v - 11** Volts
3E Front Primary Voltage drops 13v - 12** Volts

3F Rear Secondary Steady Voltage 13.5 Volts
3H Front Secondary Staedy Voltage 13.5 Volts

Shitty stock wiring harness, bad grounding, crap alternator.

Reground your wiring harness under the dash and perhaps run new wires to the injectors. Just do it right if you do.

+1 ^^^

You must remember that the voltage going to the injectors is pulsed DC. It will not measure a constant voltage. The injectors are driven by the ECU. Grounding as per TehMonkay is a good start.

I had regrounded, new alt, and new battery. I will recheck my grounds though. I also checked the continuity on the injector lines and they where fine.

Is it the ECU that controls the voltage?

The ECU just provides a ground - the power for all the injectors is the same. I'd focus on the ground below the intake manifold and the ground(s) at the computer.

Search for the 3800RPM hesitation and use the solution given, it may help.

Since you're fooling around with the computer and checking voltages and its already accessible, swap in another computer (if you can). Could be the circuitry inside.

Lastly, the voltage shown will vary depending on the pulse width that the computer is giving while the engine is running, so do another check of voltages with the engine off (ign. on). If this is the problem, the culprit is a sensor (TPS?), giving the computer wrong info.

Did that the other day.

Did this a while back and it took it out. This is a different buck at 2800rpm.




I have 720s all the way around and am runing the Rtek. I have 550's on the way and have a old comp I will plug in when they arrive.


Checked TPS.

It just seems wierd that the Voltage to the primary injectors only would steadly drop as I appraoch 2800 rpm 2-3 volts, and then kick back up after I about 3k. @-3 volts is a aweful lot I would think.

maybe the injectors are bad, did you test them according to the fsm?

Sounds like an ECU issue to me.

In most EFI systems, the power for the injectors comes from the same single source inside the ECU and is split to feed all of them. In the case of a Haltech for example - you actually split the feed wire yourself.

I'm not sure how the RTEK distributes the voltage exactly, but if its setup like most EFI systems, 1 source feeds all 4 injectors. Meaning if one is getting less than another, is a problem with where the voltage gets split....inside the unit.

Alternatively it could be a wire grounding out and having voltage sapped prior to the injector, however trimming 1-3 votls off the total doesn't sound alot like a short.

Beats me, I'd point my finger at the RTEK.

You explained that well, thank you. I have been battling this for months, MONTHS. It is just annoying for a few hundred RPM and not noticable if I rev quickly past 2800. But I can not stand it. I can not wait to swap in my old ecu and see if the problem goes away. Just waiting for some 550cc inj to come in.

what are you using to measure this?? a dmm will average it out, you should really be current ramping this on a vantage or other digi scope

A typical volt meter I guess. I see, the Vantage will give a graph. Nice. But the draw is very noticable on this meter. I can understand several .point over time. But 2-3 volt drop seems like alot.

Gee Willikers. A lot of bad answers to your question.

Your looking at the voltage drop as the injectors are having a gnd pulsed to them. If you really *get on it*, you should see the voltage drop to as low as 6-7 volts til the secondary's come on then it'll (Primary) go back up a few volts.

There is NOTHING unusual as to what your seeing. Next time watch the SECONDARY voltage. I'tll stay in the 13's til you hit 3600-3800rpm then will drop like a rock to say 7vdc or so.

IN other words it's all working like it should as far as the voltage dropping the more you *get on it*.

I just repeated what PFSANTOS said. Kinda just scanned the thread at first and missed that.

Tell you what, I can't ever remember seeing voltage drop as low as 2-3 vdc, and I've watched the voltage drop on my car a number of times.

Kinda dumb thing to ask, but your sure you have the RTEK set to 720/720? Probably yes.

Got a wideband to go with this? Probably seeing in the 9afr range when it does that....or worse. Nines and tens suck.

Been fooling around with the afm spring any in the past?

Actually just wait til the 550's show up and try them and see what happens.

Quick queation. What air filter are you using? Stock? Aftermarket? Clean?

Another quick question. What altitude is your ATP sensor set at?? Or is it not being used for something else. If not being used for another thing, forget this question. I have noticed if the ATP altitude is set at a higher altitude the fuel mixture is leaned out a bit.

Thanks Hailers.