If you skip the blow-by check, you may buy an engine that needs a major overhaul soon after it arrives. High blow-by means rising oil consumption, contaminated oil and lost power, and it often ends in a teardown. That is downtime, an unplanned bill and a genset that never earned its price.
USP&E Helps You Read Blow-By Before You Buy
We know that a used engine’s history is often incomplete. USP&E has delivered 150+ power projects in 45+ countries, with 25,000 MW contracted since 2002, and our 400+ engineers and project managers inspect, test, refurbish and maintain diesel gensets, and plan the step to gas turbines when it fits. Our systems are ISO 9001 and ISO 45001 certified, and every deal runs under FCPA and OFAC controls. USP&E is a full-service EPC and O&M contractor, not a broker.
You do not need to strip the engine. You need a proper blow-by test under load, a few supporting checks and someone who can tell you what the readings mean for your purchase.
Test Blow-By the Right Way
Measure blow-by with a flow meter on the crankcase breather while the engine runs under load at normal temperature. A test at idle tells you little; worn rings show up when cylinder pressures are high.
Compare the reading with the engine maker’s guidance for that model and with readings from similar engines. Blow-by rises naturally with wear, so the question is where this engine sits on that curve. Record the load, speed and temperature with every reading.
Look at the breather and crankcase too. Heavy oil mist, oil around the breather outlet or pressure pushing out the dipstick are warning signs, even before you read the meter. Units from our used diesel generator inventory are tested this way before sale.
Back Up the Reading With Other Checks
Blow-by alone does not tell the whole story. Pair it with oil analysis for fuel, soot and wear metals, oil consumption records if the seller has them and a compression or leak-down test where the engine design allows.
Check fuel burn against output. A worn engine often burns more fuel for the same load. The figures in our fuel consumption chart for diesel sets help you judge whether consumption looks reasonable for the size and load.
Put all the evidence together before you decide. High blow-by with clean oil and good compression may point to a breather problem. High blow-by with rising oil use and wear metals points to worn rings and liners, and a price that should reflect a coming overhaul.
Plan Your Fleet and the Gas Turbine Path
Use blow-by readings across your fleet to plan overhauls and replacements. Engines with rising readings can be scheduled for work before they fail, and the oldest units can be retired as new capacity arrives. Marine units bought from our marine generator stock deserve the same checks.
Many operators now pair diesel fleets with gas turbine generators for base load. Options include a remanufactured GE Frame 6B, verified used/new gas turbines, natural gas engines/stations and New USP&E FX-45 45MW Modular Gas Turbine for the Hyperscale Data Center sector in the USA. In hyperscale EPC/O&M, AI gas turbines, hyperscale generators and gas turbines for compute call for the same evidence-led buying.
Buy on evidence, not hours on a meter. A genset with sound blow-by readings is a solid asset; one without is a gamble. For larger quantities, see our sister site on wholesale diesel generators.
Where USP&E Supports Your Used Diesel Genset Project
For your used diesel fleet transition, your engineering lead sits at USP&E’s Executive HQ in Johannesburg (22 Kildoon Rd, Bryanston), with Cape Town (31 Brickfield Road, Woodstock) adding design, commissioning and project depth. Southern Africa is where USP&E plans, controls and supports frontier power work across the continent.
London (162-168 Regent Street) structures finance and contracts for inspected used diesel gensets and gas turbine bridges, Colorado Springs (1755 Telstar Dr, Suite 300) and Knoxville (800 S Gay St, Suite 700) connect you to US equipment supply and US-based engineering, and Wuxi, China (No. 1, Ningzhou Road, Wuxi) follows up China manufacturing and supply chain.
For blow-by checks, Johannesburg and Cape Town technicians can test used gensets under load on site, review oil and fuel evidence and tell you what the readings mean before you buy. Regions served: USA | AFRICA | UK | UAE | CHINA. Reach matters more than pins on a map: 150+ power projects in 45+ countries, 25,000 MW contracted since 2002, and ISO 9001 and ISO 45001 certified.
What USP&E Has Delivered for Used Diesel Genset Buyers
You want proof that USP&E has supplied and tested diesel gensets for demanding sites. These projects show that record.
- USP&E supplied 28 Cummins KTA50 containerised diesel gensets, 1,275 kVA each, for Perseus Mining’s Nyanzaga Gold Project in Tanzania.
- Zondereinde platinum mine, South Africa: USP&E supplied, packaged and serviced six zero-hour surplus Wabtec GE16V250 gensets, giving the mine 25 MW of base-load power through Eskom load shedding. Read the case study.
- Kinross Gold, Tasiast, Mauritania: USP&E supplied and installed a Caterpillar backup power station of low-hour Cat 3516B gensets with new switchgear, on time and on budget. Read the case study.
HowTo: Check Blow-By on a Used Diesel Genset
Your 3-step plan: 1. Share the genset details, seller records and test access. 2. Receive a blow-by test, supporting checks and condition report. 3. Buy, refurbish or pass, then plan your gas turbine path.
- Ask the seller for oil analysis, running hours and any previous blow-by readings.
- Run the genset to normal temperature under load.
- Measure blow-by with the correct meter and record load and temperature.
- Look for oil carry-over, smoke and crankcase pressure alarms.
- Compare the result with the engine maker’s limits and similar engines.
- Use the result to price repairs or plan the move to gas turbines.
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FAQ: Used Diesel Blow-By Check Path to GT
What is crankcase blow-by on a diesel engine?
USP&E describes blow-by as combustion gas that leaks past the piston rings into the crankcase. All engines have some, but it rises as rings and liners wear. Measuring it under load is one of the clearest ways to judge the internal condition of a used engine.
How is blow-by measured?
USP&E measures blow-by with a flow meter on the crankcase breather while the engine runs under load at normal temperature. Readings are compared with the engine maker’s guidance and similar engines, with load, speed and temperature recorded so results can be compared over time.
What does high blow-by mean when buying a used genset?
USP&E treats high blow-by as a warning of worn rings or liners, especially with rising oil use and wear metals in oil analysis. It often means a major overhaul is coming. The purchase price should reflect that cost, or the buyer should walk away.
Can high blow-by have other causes?
USP&E checks for other causes such as a blocked or faulty breather, a damaged turbocharger seal or a test done at the wrong load or temperature. Pairing blow-by with oil analysis and compression tests separates these causes from true ring and liner wear.
Where are USP&E’s offices for used genset inspections?
USP&E supports used genset inspections from Johannesburg and Cape Town, with technicians who reach sites across Africa. London structures contracts and finance, Colorado Springs and Knoxville support US gas turbine supply and engineering, and Wuxi follows up equipment made in China.
Has USP&E delivered diesel gensets before?
USP&E supplied 28 Cummins KTA50 containerised diesel gensets, 1,275 kVA each, for Perseus Mining’s Nyanzaga Gold Project in Tanzania. Public case studies also include zero-hour surplus gensets for the Zondereinde mine and low-hour Cat 3516B gensets for Kinross at Tasiast.
Is USP&E a broker for used gensets?
USP&E is not a broker. USP&E inspects, refurbishes, installs and maintains gensets with its own technicians and engineers, so the team that tests your blow-by is the same team that stands behind the engine and answers for it. No middleman sits between you.
How fast can USP&E respond to a pre-purchase test request?
USP&E can review the genset details and seller records as soon as you share them, then plan a test visit with the right meters and oil sampling kit. Engineers report the findings quickly so you can decide before the seller moves on.
Buy the Engine, Not the Story
Check blow-by and your used genset arrives with known condition and a fair price. Skip it and a hidden overhaul can wipe out the savings. USP&E will help you test, decide and plan with confidence.
Talk to an engineer about your used diesel fleet transition: use the USP&E contact page, call +27 10 822 2324 or email info@uspeglobal.com. You can also search the USP&E inventory for equipment that fits.
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