Precision 1000cc Injectors Won’t Start: Crome Dead Time Offset Explained
The No-Start That Confused Everyone
Swap in a set of 1000cc injectors, key the engine, and nothing happens. No fuel smell on the plugs, no stumble, just a cranking engine that refuses to fire. The fuel pump runs, the injectors click, and the ECU looks fine. This particular no-start is almost always the injector dead time — called “offset” in Crome — and it has to match the new injectors exactly before the engine sees any meaningful fuel at all.
What Injector Dead Time Actually Is
Every fuel injector has a mechanical lag between the moment the ECU sends its open signal and the moment the pintle actually lifts and fuel starts flowing. That lag is the dead time. It is real, measurable, and different for every injector design.
The ECU compensates by adding extra pulse width equal to the dead time. Without that correction, the injector fires shorter than commanded. At light load the error is small. At a very short commanded pulse width — like when cranking a cold engine — the actual delivered fuel can be nearly zero. The ECU thinks it is squirting; the injector barely cracks open. That is your no-start.
Dead time also changes with battery voltage. Lower voltage means slower solenoid actuation and a longer lag. A properly calibrated dead time table has values at each voltage step from roughly 8V up to 16V, not just one single number.
Why the Precision 1000cc Injectors Specifically
Precision Turbo’s 1000cc injectors are low-impedance units, typically around 2.4 ohms. Running them with 10-ohm inline resistors is the standard approach on an OBD1 Honda ECU, which uses a saturated high-impedance driver circuit. The resistors limit current and protect the driver transistor. That part of the setup works fine — it was already proven over two years on the 450cc injectors the owner was replacing.
The problem is that the Precision 1000cc units have a substantially different dead time than the 450cc injectors. When Crome still had the offset values from the old injectors loaded, the timing was completely wrong. At crank speed with a short commanded pulse, the injector never meaningfully opened. No fuel. No start. The fix is selecting the Precision 1000cc preset in Crome’s injector selection table and setting the offset to values in the 110-range. With those dialed in, the ECU’s commanded pulse width starts translating into actual fuel delivery.
Setting Injector Offset in Crome
Crome handles injector dead time through two related settings: the injector selection, which loads a base dead time table, and the injector offset, which is a trim on top of that base. The general process:
- Open Crome and go to injector setup via the fuel tools plugin. Select your injector from the dropdown. If the Precision 1000cc is listed, use that preset — it pre-fills the dead time table with manufacturer data.
- The injector offset field is a coarse trim. The Precision 1000s need values around 110 for the engine to start and idle. If you are starting from scratch with an unknown injector, begin on the high side and work down — running rich during initial startup is far safer than lean.
- The offset and the fuel multiplier are separate adjustments. The multiplier scales total fuel delivery for injector size. The offset corrects for mechanical lag. Mixing them up wastes hours chasing the wrong table.
The Voltage Table — the Part People Miss
Getting a car to start and idle on a single offset value is only half the job. Dead time varies with voltage, and the charging system does not stay at a flat 14V. When the cooling fan kicks on, voltage can drop half a volt or more. Headlights on, same thing. Each drop lengthens the injector’s mechanical lag, and if the dead time table does not account for it, the mixture goes lean at the exact moment electrical load increases.
A complete dead time table has entries at each voltage step — 8V, 10V, 12V, 14V, 16V or similar. If the car idles cleanly but stumbles or leans out when the fan or AC compressor engages, the voltage compensation entries are off. Reference the manufacturer’s published dead time data where available, then use a wideband to trim each voltage step while deliberately varying electrical load.
Fuel Table Scaling for a Bigger Injector
A 1000cc injector flowing through a table scaled for 450cc will flood the engine. Crome’s fuel tools plugin recalculates the Final Multiplier automatically when you change injector size — but verify it actually updated when the injectors were swapped. If it did not, even with perfect dead times, the engine will run extremely rich and may not idle at all.
Start with Crome’s auto-scaling result, confirm the multiplier looks proportionally correct, then trim at cruise and idle with a wideband. Large injectors at idle are notoriously fussy — small pulse width variations have a bigger effect on AFR than they did with smaller injectors, so patience during idle trimming pays off.
Low-Impedance Injectors and Inline Resistors on OBD1 Hondas
The OBD1 Honda ECU — P28, P30, and similar — uses a saturated driver circuit designed for high-impedance injectors around 12 ohms. Running 2.4-ohm low-impedance injectors directly into that driver overloads the transistor. Over time it fails. Inline resistors bringing total circuit resistance to roughly 12 ohms protect the driver and are the standard fix for low-impedance injectors on these ECUs.
The alternative is a peak-and-hold driver module, which actively manages current — faster opening, better atomization at low pulse widths, more hardware to wire in. For a street or track car on Crome, the resistor approach works well as long as the resistors are correctly sized and the injector offset is properly calibrated.
One thing to keep in mind: inline resistors do slightly alter the effective dead time compared to running the same injector on a dedicated peak-and-hold driver. If you import dead time data from another platform where those injectors were calibrated on a P&H system, expect some deviation and plan to fine-tune the table from that starting point.
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