SureTrack Community Fix: Cool Fuel isn’t Cool

Real Fixes from Mitchell 1’s SureTrack® expert information resource are documented issues from actual shop repair orders and community discussions. Read on to see how SureTrack can help you correct issues that are not easily diagnosed using OEM information alone. SureTrack is available at no additional cost in our ProDemand product.


One of the biggest problems a diesel-powered vehicle can experience is contamination of the fuel, usually with water. These vehicles usually have a light that will let you know if there is water in the fuel. SureTrack community member noarsons had a 2000 Ford F350 Super Duty in their shop that had the Water in Fuel light on, but it actually had coolant contaminating the fuel. They posed the question to the community, and with the help of fellow community member powerstroketech and others, they were able to resolve the issue quickly.

The following Community Fix summarizes the interaction between members of the community that led to the solution.

Vehicle
2000 Ford Pickup F350 Super Duty 7.3L

Title
Coolant in the fuel, replaced injector cups.

Complaint
Customer complains that Water in Fuel light is on.

Diagnostic Steps Performed/Parts Replaced
Confirmed that Water in Fuel light is on. Took sample and it appears to have coolant in the fuel. Injector buzz test good. Contribution test shows #8 misfiring or P0284. What I have seen before is fuel in the coolant. I have a 7.3l with 370000 miles which has coolant in the fuel. Leaning towards injector sleeves but with that you usually see fuel in the coolant. Any one else seen this?

Best Answer from Community Member powerstroketech
How does the engine run? What is the fuel pressure? If the fuel pressure is less than the cooling system pressure at normal operating temp., the higher pressure will over take the lower pressure. Also, when the engine is turn off after driving, the cooling system will maintain pressure, where as the fuel pressure can leak down. I agree with you, most of the time when injector cups fail, it puts fuel in the coolant. It is possible though, that is can put coolant in the fuel. To verify this you could pressure test the cooling system with the fuel return line removed from the fuel filter housing and monitor it for coolant or air. If you can not see anything, then place a balloon or cut a finger off of a pair of latex gloves and place it over the fuel return port while pressure testing the cooling system.

Cause
After further review, found #8 and #5 injector cups leaking.

Correction
Replaced all injector cups in the vehicle using the proper removal and installing tool.


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About the Author

Nick Taylor

Nick Taylor is the SureTrack Community Administrator and a Senior Applications Specialist at Mitchell 1 with over 25 years of experience with electronic repair data systems. Nick previously worked in the automotive dismantling and engine rebuilding industries.