Upgrade your current tester gauge to one that is more accurate and can tolerate more abuse.
This rugged, stainless steel gauge can survive much more abuse than non-liquid-filled gauges. Many don't realize just how fragile the mechanism that moves the needle is. If you bang the gauge around or let it rest on the engine while running, the mechanism can be disrupted, giving you inaccurate readings. FIT
160 PSI Liquid Filled Fuel System Pressure Gauge w/ Adapter Fitting
$20.00
SKU:
TUL-160PSI 
Product Details
This will fit almost all pressure testers on the market. The gauge has a 1/4 inch NPT male thread, and the brass adapter included will allow you to connect it to a 1/8 inch NPT female thread.
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Sale
$78.00
1976 to 1993 Bosch C.I.S. Fuel Injection Pressure Tester - Builders Kit
NEW! FIRST 10 SOLD on sale. For K-Jetronic and KE-Jetronic fuel injection. Basic kit without extras. Video training manuals purchase separately. Attachment to test D-Jetronic can be purchased separately.
The email questions from owners trying to get their old fuel-injected 1970 to 1993 Mercedes running right drive him crazy. Most follow a pattern, and most will require a fuel injection system flow and pressure test to troubleshoot the problem.