Top 10 Holley Sniper EFI Tech Tips
Holley Technical Training Manager Tom Kise's top ten "suggestions" for Holley Sniper EFI System installation issues. This is great information that can only get you closer to an ideal solution. If there is anything you see here that needs clarification please Contact Us.
Check these EFI Tech Tips before you call Tech Support
If you are having issues with your Sniper Fuel Injection install, go through these common issues first, before getting stuck on hold with Tech Support. They will ask you if you have tried these tips before anything else. If you have not already looked into tip #2 you will be hanging up and calling them again. Always try to fix mechanical issues with your car before installing an EFI system and always follow the instructions.
- Read the Instructions
- Check Your Wiring
- Double-Check Your Ground
- Triple-Check Your Ignition
- Inspect Your O2 Sensor
- Fuel Pump Location
- Idle Air Control Valve
- Hard Starting Issues
- Ignition Switch Wiring
- Strange Noises
Read the Instructions
- #1 READ the instructions and Follow them. If you do not understand a step, seek assistance.
Check Your Wiring
- #2 Wire it properly… Most important! MAIN POWER AND GROUND need to go to the battery! Direct to the BATTERY! Not to the fuse panel, starter solenoid or some random distribution stud or strip or other location. Direct to the battery means to the battery. Make sure you are using proper wiring practices; incorrect connections will result in excessive resistance. Resistance results in heat and heat results in more resistance. A common issue we see is a result of poor fuel pump grounding running an eyelet from the pump to a rusty or painted surface. The resulting resistance can burn up fuel pumps, wiring and relays. Extending wires with too small of a wire gauge will also result in the same damage.
Double-Check Your Ground
- #3 Engine ground should be 1AWG or larger and go directly from the battery to the engine. Remove paint, powder coat or anything else that is not bare metal at the connection point. Grounding the battery to the frame and the frame to the engine may have been OK for your carburetor, but it is not sufficient for digital electronics.
Triple-Check Your Ignition
- #4 Ignition parts - with EFI you need to run resistor plugs and resistor, non-solid core wires. Be sure you have properly gap your spark plugs and if you plan to run Magnetic pickup distributors for timing control, you need to properly phase the rotor. Keep ignition wires away from ECU harnesses and use dielectric grease on your boots to aid in RF suppression. If you have RF and or EMI issues you need to correct them or they will result in drivability issues including idle control problems and could possibly damage the ECU. Have you ever watched a post-nuclear apocalypse movie? EMI is what wipes out all the electronics they were not defective they were damaged. Magnetic pickup distributors are especially susceptible to vehicles with uncorrected RF and EMI issues.
Inspect Your O2 Sensor
- #5 O2 sensors… The Sniper ships with an OEM grade Bosch O2 sensor. Oxygen sensors read unburnt Oxygen, not Fuel. All it knows is what it sees in the pipe. When a wideband sensor is damaged it will almost always reads dead lean. Why; because the sensor gets fouled and exhaust gasses cannot get to the sensing element leaving oxygen as the only thing present for it to read, hence the dead lean reading.
- So, what damages O2 sensors? Top cause is excessive fuel, most often caused by the system adding fuel due to false readings resulting from incorrect sensor placement, cylinder misfires, exhaust leaks, overly rich tunes. You may be surprised to know that excessively rich engines can cause a false lean reading, resulting in a closed loop adding even more fuel making it read leaner and adding more fuel until it floods the engine and fuel fouls the sensor.
- Oil control, if you're burning oil you will kill your O2 sensor, closed loop chasing unstable fuel supply issues (see fuel pumps comment) wrong sealants or fuel additives that are not O2 sensor safe will kill your sensor. The O2 needs to be mounted 6-8” after the merge in the header collector. It needs the tip pointed down at least 10 degrees from horizontal and at least 15 degrees from vertical I prefer about a 45-degree angle from horizontal. You should then have at least 18-24” of pipe after the sensor.
- If you have any exhaust leaks between the combustion chamber and 18-24” after the sensor you are going to have problems.
- Pinched and burnt O2 sensor wiring, keep it high tight and safe, if you short the harness, not only are you likely to damage the sensor you probably just short-circuited your ECU. For the most part all you need is a solid foundation. Fix mechanical issue before installing the system and follow the instructions.
Fuel Pump Location
- #6 Where is your Fuel pump? The sniper master kits ship with OEM grade 255 LPH Walbro Pumps. Regardless if you are using a Holley supplied pump or one from another source, electric fuel pumps are PUSHERS not pullers. The pump needs to be GRAVITY FED. Meaning the pump inlet needs to be at or below the bottom of the tank and as close to the tank as possible. This is why most OEM EFI pumps are in the tank. It needs to have an 80-100-micron pre-filter installed between the tank and the pump in addition to a 10-micron filter between the pump and throttle body.
- Avoid using any 90-degree fittings between the tank and pump. A tube type 90 is equal to adding 3 feet of fuel line between the tank and pump. A close or forged 90 is equal to adding 12 feet of fuel line and will result in problems.
- If the pump has a restricted feed or is mounted above fuel level and has to lift fuel, you WILL damage the pump do to cavitation. Most current pump fuels boil around 130 degrees. Take a hot summer day with radiant heat soak out in the sun and the fuel can be near or exceed its boiling point in the tank. If vacuum is required to overcome a restriction or to lift the fuel to a high mounted pump, the resulting reduction in pressure can and will boil fuel in the line and at the pump inlet resulting in fuel pressure issues and pump damage. If your pressure drops, the system will react by adding fuel in closed loop and learn. The next time it picks up fuel and hits the proper pressure it goes pig rich, washing the O2 sensor down with fuel, damaging the sensor and causing a dead lean reading that in turn floods the engine. The resulting O2 sensor failure is damaged not defective.
- How did you install the return line to the tank? If you free dumped it in the top, it will aerate and foam up the fuel. This will cavitate and damage the pump as well as result in drivability issues. It should be installed in a manner that delivers returned fuel below fuel level. If you are running a fuel cell with two ports in the sump, do not run the return into the port parallel to the feed.
- Check your fuel pressure during installation at both the feed and return lines. Feed pressure should be knocking on 58 PSI and the return should ideally be zero, if the feed pressure is not correct, or if the return line pressure is greater than 4-5 PSI find and correct the restriction before proceeding.
Idle Air Control Valve
- #7 Idle / IAC… I want to start by saying that the engine should not require any IAC air bypass to idle. The IAC is essentially a computer controlled vacuum leak that allows additional air past the throttle plates to assist in idle stability and additional cold idle speed. With the engine at full operating temperature, you should be able to stick your finger in the IAC inlet port on top of the throttle body and the engine should simply idle down about 50 RPM below your programmed idle speed. If it dies or drops more than 50-75 RPM, the throttle is closed too far. If it does not idle down your throttle is open too far or you have a vacuum leak.
- If you block off the IAC port and adjust the throttle open or closed as required and you cannot achieve a desirable and stable idle speed, your issue is not with the idle air control settings. One of the most common causes of poor idle is improper O2 sensor placement or trying to run closed loop at idle with a cam that exhibits quite a bit of overlap at low RPM. Both of these are easily corrected.
- Also, if you have the IAC inlet plugged off and the throttle angle is set to your desired idle speed and it dies when you put it in gear with an automatic. Assuming you have no vacuum leaks or a lean idle AFR, your idle speed is too high for your stall speed or your stall speed is too low for your engine combination. Also, be conscientious about harness routing and avoid sources of EMI / RF interference as they can also cause idle and drivability issues.
Hard Starting Issues
- #8 Hard starting and hot restart issues. Make sure the fuel pump is properly mounted and picking up fuel. If you turn your key to run, and the RPM on your tach sweeps, you probably have an MSD 6425 digital 6AL or ready to run distributor with the 12V square wave tach output wire. Most likely, you missed the part in the ignition system or distributors instruction manual that said you need to disable your ignition systems rev limit verification feature if you are running EFI. If not, you will fight startup issues. Flood the engine and damage your O2 sensor. Also check your cranking voltage if it starts hard. If your voltage drops below 11 volts replace the battery with one capable of supporting the vehicles cranking needs ideally it should not drop below 12 digital electronic like clean stable voltage if you’re getting in the 10's you’re asking for issues.
Ignition Switch Wiring
- #9 Incorrect ignition switch wiring. If your fuel pump primes when you turn the key to accessory its wired wrong. (This could have been lumped in with #8 but I felt it needed a place of its own.) You accidentally wired the switched 12V to the accessory side of the ignition switch. This circuit shuts off during crank and will obviously cause problems.
- Your handheld should stay powered on between run and crank if it shuts off it is wired wrong or you have a dead spot in the switch. If the switch has an engineered dead spot between run and crank (It did not matter with a carburetor when they designed your vehicle, but it’s not EFI friendly) and it’s just not plum worn out, you can install a time delay relay in-line to correct this I use relay part number 74985 from Delcity. To overcome the switch design.
- #10 Weird sounds…. Clicking, ticking and sucking sounds. Many of these are completely normal with EFI. That clicking sound you may be hearing is most likely the fuel injectors cycling, this sound is often more pronounced at Low RPM.
- Part throttle sucking sounds. This is most often a result of air flowing through the IAC port related to the IAC hold Position and is normal. Another cause may be the proximity of a dual plane intakes plenum divider to vacuum passages under the throttle body resulting in an odd sucking or whistling sound. While it may sound odd, it is not a defect and will not cause any drivability issues. Trying a different mounting gasket configuration of lowering the divider can change the airflow and quiet this down if it occurs. This happens with some carburetors on dual planes as well. Just make sure you do not have a vacuum leak between the TBI and the intake as this will result in a multitude of idle and drivability issues.
Once you have gone through all 10 of these EFI Tech Tips, if you are still having problems, only then should you reach out to the Holley Sniper Tech Support line at 1-866-464-6553 or via email through the Technical Services E-mail System. Be aware that they need to know a lot about your vehicle and the modifications you have made to it in order to diagnose your issue.
If you still are having issues with the EFI kit you purchased from us please Contact Us and we'll do our best to help you out.