Precision 1000cc Injectors Won’t Start on Crome: The Offset Dead Time Fix
The Offset Is the Problem — Here’s Why It Has to Be So High
If you’ve swapped to Precision 1000cc injectors on a Honda running Crome and the car won’t start, the injector offset is almost certainly the culprit. A lot of tuners try values in the 30–60 range because that works for smaller injectors, but with 1000cc low-impedance units and inline series resistors, the offset often needs to climb to around 110 before the injectors open long enough to deliver any fuel at all.
What Injector Dead Time Actually Is
Every fuel injector has a lag between when the ECU sends a fire signal and when the pintle actually lifts off its seat. That gap is dead time — called injector offset in Crome.
During dead time, no fuel flows. The ECU has to hold the injector command open for at least that long before the pintle moves. If the offset in the tune is shorter than the injector’s real dead time, the effective pulse width is zero. The pintle never opens. The engine gets no fuel — no start, no fuel smell on the plugs, exactly what the thread describes.
Set it right and the injector opens. Set it too low and you’re cranking on a dry engine.
Why Honda OBD1 ECUs Need Resistors With Low-Impedance Injectors
Honda OBD1 ECUs use a saturated-drive injector circuit designed for high-impedance injectors around 12 ohms. Low-impedance injectors — typically 2 to 3 ohms — draw far more current through the same driver circuit. Without compensation, that excess current overheats the injector driver transistors. Run low-impedance injectors on an OBD1 Honda without a resistor pack and you’ll burn up the ECU’s injector drivers over time.
The fix is wiring resistors in series between the ECU and each injector, raising total circuit impedance to a safe level. Ten-watt, 10-ohm resistors are a common choice — exactly what the thread describes running. That’s correct practice for this application.
How Series Resistors Change the Dead Time
Here’s where it gets counterintuitive. Adding resistance slows down the current rise through the injector’s solenoid coil. The injector opens when the magnetic field builds enough to pull the pintle — but with extra resistance in the path, that field builds more slowly. Longer time to build the field means longer dead time.
This gets compounded with 1000cc injectors because they have a physically larger solenoid than a 450cc unit. More wire, more inductance, more time required to generate sufficient magnetic force. A large solenoid plus 10 ohms of series resistance is a combination that pushes opening latency far beyond what the same resistors would cause with a smaller injector.
The offset that worked for the 450cc injectors isn’t even close to what the 1000cc injectors need. They’re not just bigger — they behave differently through the same circuit.
Crome’s Injector Selection Table
Crome uses the injector selection to set the base flow rate for fuel table scaling. If you’re still on a 450cc selection while running 1000cc injectors, every pulse width the ECU calculates is wrong before dead time even enters the picture.
Select the Precision 1000cc entry from the dropdown if it’s available. If your exact injector isn’t listed, type 1000 into the field and press enter — Crome accepts manual entries. Get the selection right first. Then address the offset.
Finding the Right Offset for Your Setup
There’s no single correct offset number for “Precision 1000cc with 10-ohm resistors.” Dead time varies with battery voltage, fuel pressure, and injector batch. The strategy is to start high enough that the injectors actually open, confirm a start, then refine.
- Set the offset high enough to fire the engine — around 110 is where it worked in this case
- Once running, check idle quality and air-fuel ratio
- If idle is rich and stumbles at light throttle, bring the offset down in small steps
- If the car still won’t start, go higher — some large-solenoid injectors with series resistors need more
Offset is the coarse correction. Fine tuning at idle and cruise comes from the fuel multiplier and individual fuel table cells after the engine is actually running.
Scaling the Fuel Multiplier After a Big Injector Swap
Going from 450cc to 1000cc more than doubles the injector flow at any given pulse width. If the fuel multiplier isn’t scaled back to match, the engine floods on the first crank attempt — which means you’re pulling plugs and airing out cylinders before you even get a data point.
Before cranking with the new injectors, pull the fuel multiplier down significantly from whatever it was tuned to with the 450s. A rough first cut is around half the previous value. That’s a starting point, not a final number — tune it up from there once the engine runs and you can watch an air-fuel gauge.
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