Common Onan 5500 & 7000 RV Generator Problems

Carbureted and EFI are not the same machine

Depending on model and spec, 5500 and 7000-class gasoline Onan generators may use a carbureted fuel system or electronic fuel injection. The engines have a lot in common; the fuel systems do not.

A carbureted unit meters fuel mechanically through jets and passages, so it is sensitive to varnish and debris. An EFI unit meters fuel electronically and has different components, different diagnostic points and different failure modes. Applying carbureted logic to an EFI unit — or the reverse — wastes time and parts.

Identifying the exact model and spec number is the first step on these units for exactly this reason.

Specifications, components and procedures vary by model and spec number. We confirm the specific unit before diagnosing or quoting parts.

No-start

Cranking without starting has the same broad categories on these units — fuel, ignition, cranking speed, safety circuits and controls — but the fuel-side testing differs between carbureted and EFI configurations. See cranks but won't start.

Fuel delivery

Both configurations depend on adequate fuel supply from the coach tank through the filter and pump. Restrictions, weak delivery and air leaks affect both. On carbureted units, a deteriorating pump can also affect the carburetor downstream.

Surging

Unstable RPM on a carbureted unit usually leads to metering and fuel delivery. On EFI units, unstable running is diagnosed through the fuel and control system rather than by cleaning jets. See generator surging.

Shutdowns

Starts and dies, or runs then quits — see starts then dies. Retrieve stored fault information first; on these controllers, code 36 is common with unexpected shutdowns.

Load problems

These units are typically running two air conditioners plus household loads. Failures that only appear under real power are common, and load testing is how they're found — see dies under load.

Control and electrical

Connections, grounds, sensors and controller-side faults all affect running and shutdown behavior, and matter more on units with more electronics involved in fuel control.

Maintenance

Oil, filters, air filter, plugs where applicable and regular exercise per your owner's manual. Annual generator service keeps these units in the condition where small problems get caught before they strand you.

When replacement makes more sense than repair

Occasionally a unit reaches the point where the repair cost exceeds what the generator is worth. When that happens we say so, and we can discuss refurbished RV generators as an alternative.